Gr11 Chemistry M2 PDF 2017 (Papua New Guinea)

DEPARTMENT OF EDUCATION GRADE 11 CHEMISTRY MODULE 2 CHEMICAL AND METALLIC BONDING PUBLISHED BY FLEXIBLE OPEN AND DISTANCE EDUCATION PRIVATE MAIL BAG, P.O. WAIGANI, NCD FOR DEPARTMENT OF EDUCATION PAPUA...

DEPARTMENT OF EDUCATION GRADE 11 CHEMISTRY MODULE 2 CHEMICAL AND METALLIC BONDING PUBLISHED BY FLEXIBLE OPEN AND DISTANCE EDUCATION PRIVATE MAIL BAG, P.O. WAIGANI, NCD FOR DEPARTMENT OF EDUCATION PAPUA NEW GUINEA 2017 Writer Honeylet Akiatan Content Editors Science Department Subject Review Committee Language Editor Dr. Steven Winduo Course Format Editor Joydee Mabbagu GR 11 CHEM M2 TITLE GRADE 11 CHEMISTRY MODULE 2 CHEMICAL AND METALLIC BONDING IN THIS MODULE YOU WILL LEARN ABOUT: 11.2.1: ATOMIC STRUCTURE 11.2.2: PERIODIC TABLE 11.2.3: BONDING AND STRUCTURE 1  GR 11 CHEM M2 ISBN AND ACKNOWLEDGEMENTS Acknowledgement We acknowledge the contributions of all secondary teachers who in one way or another have helped to develop this Course. Our profound gratitude goes to the former Principal of FODE, Mr. Demas Tongogo for leading FODE team towards this great achievement. Special thanks to the staff of the Science Department of FODE who played active roles in coordinating writing workshops, outsourcing lesson writing and the editing processes involving selected teachers of Central Province and NCD. We also acknowledge the professional guidance provided by Curriculum and Development Assessment Division throughout the processes of writing and the services given by members of the Science Review and Academic Committees. The development of this book was co-funded by the GoPNG and World Bank. DIANA TEIT AKIS PRINCIPAL Flexible Open and Distance Education Papua New Guinea Published in 2017 by Flexible Open and Distance Education ©Copyright 2017, Department of Education, PNG All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means electronic, mechanical, photocopying, recording or any other form of reproduction by any process is allowed without the prior permission of the publisher. Printed by the Flexible, Open and Distance Education ISBN 978-9980-89-504-2 National Library Services of Papua New Guinea 2  GR 11 CHEM M2 CONTENTS TABLE OF CONTENTS Page TITLE ……………………………………………………………………………… 1 ISBN AND ACKNOWLEDGEMENTS ………………………………………………………………………. 2 TABLE OF CONTENTS ……………………………………………………………………………… 3 SECRETARY’S MESSAGE ……………………………………………………………………………… 4 MODULE 11.2: CHEMICAL AND METALLIC BONDING………………………………………. 5 Introduction ………………………………………………………………………………. 5 Learning Outcomes ………………………………………………………………………………. 5 Terminologies ………………………………………………………………………………. 6 11.2.1 Atomic Structure………………………………………………………………………………… 7 Relative Atomic Mass……………………………………………………………………………. 10 Electrons in Orbit……………………………………………………................................ 13 11.2.2 Periodic Table……………………………………………………………………………………. 17 The Development of Periodic Table…………………………………………………….. 17 Periodic Table Variations………………………………………………………………………. 22 11.2.3 Bonding and Structure……………………………………………………………………….. 30 Chemical Bonding…………………………………………………………………………………. 30 SUMMARY ……………………………………………………………………………… 44 ANSWERS TO LEARNING ACTIVITIES ……………………………………………………………………… 50 REFERENCES AND APPENDICES ……………………………………………………………………………… 55 3  GR 11 CHEM M2 MESSAGE SECRETARY’S MESSAGE Achieving a better future by individual students and their families, communities or the nation as a whole, depends on the kind of curriculum and the way it is delivered. This course is a part of the new Flexible, Open and Distance Education curriculum. The learning outcomes are student-centred and allows for them to be demonstrated and assessed. It maintains the rationale, goals, aims and principles of the national curriculum and identifies the knowledge, skills, attitudes and values that students should achieve. This is a provision by Flexible, Open and Distance Education as an alternative pathway of formal education. The course promotes Papua New Guinea values and beliefs which are found in our Constitution, Government Policies and Reports. It is developed in line with the National Education Plan (2005 -2014) and addresses an increase in the number of school leavers affected by the lack of access into secondary and higher educational institutions. Flexible, Open and Distance Education curriculum is guided by the Department of Education’s Mission which is fivefold:  To facilitate and promote the integral development of every individual  To develop and encourage an education system that satisfies the requirements of Papua New Guinea and its people  To establish, preserve and improve standards of education throughout Papua New Guinea  To make the benefits of such education available as widely as possible to all of the people  To make the education accessible to the poor and physically, mentally and socially handicapped as well as to those who are educationally disadvantaged. The college is enhanced through this course to provide alternative and comparable pathways for students and adults to complete their education through a one system, two pathways and same outcomes. It is our vision that Papua New Guineans’ harness all appropriate and affordable technologies to pursue this program. I commend all the teachers, curriculum writers and instructional designers who have contributed towards the development of this course. UKE KOMBRA, PhD Secretary for Education 4 GR 11 CHEM M2 CHEMICAL AND METALLIC BONDING 5  GR 11 CHEM M2 MESSAGE MODULE 2: CHEMICAL AND METALLIC BONDING Introduction We see different substances around us which are either elements or compounds. You also know that atoms of the same or different elements may combine. When atoms of the same elements combine, we get molecules of the elements. We get compounds; however, when atoms of different elements combine. Have you ever thought why atoms combine at all? In this lesson, we will find an answer to this question. We will explain what a chemical bond is and then discuss various types of atoms of different elements and variation in the periodic properties of elements. Configuration of atoms, the electronegativity difference between bonded atoms. Such as, ionic compounds result from a transfer of electrons from one atom to another which produces ions, oppositely charged atoms, that attract. Covalent compounds share a pair of opposite spin electrons; equal sharing gives a non-polar bond and unequal sharing a polar bond. Exploration of covalent bonding begins with the empirical rules of Lewis that allow for the construction of simple two-dimensional models of covalent compounds. Learning outcomes After going through the Module, you are expected to:  demonstrate an understanding of the patterns of arrangement of electrons in atoms and describe the electron arrangement in terms of shells and sub shells (s, p, d and f).  explain trends and relationships between elements in terms of atomic structure and bonding.  explain that the position of an element in the periodic table reflects its electron configuration.  draw diagrams (shells or Lewis dot) to show how ions can be formed by atoms gaining or losing electrons.  draw electronic shell diagrams to show the formation of ionic and covalent compounds.  differentiate between ionic, covalent, and metallic bonds.  explain the formation of coordinate (dative) bonds.  discuss the allotropes of carbon ( graphite and diamond).  describe the concept of metallic bonding, using diagrams.  explain the polarity and formation of hydrogen bond. 6  GR 11 CHEM M2 CHEMICAL AND METALLIC BONDING Time Frame 10 weeks This module should be completed within 10 weeks. If you set an average of 3 hours per day, you should be able to complete the module comfortably by the end of the assigned week. Try to do all the learning activities and compare your answers with the ones provided at the end of the module. If you do not get a particular exercise right in the first attempt, you should not get discouraged but instead, go back and attempt it again. If you still do not get it right after several attempts then you should seek help from your friend or even your tutor. DO NOT LEAVE ANY QUESTION UN-ANSWERED. Terminologies Allotrope Is the same element with different physical properties. Atom Is the smallest particle of an element. Atoms of different elements may also combine into systems called molecules, which are the smallest modules of chemical compounds. The total number of protons (positively charge) in a given atom determines the atomic number of an element. Atomic mass or mass number Is the sum of an atom's protons and neutrons that are always expressed in whole numbers. Atomic number Is the number of protons (also number of electrons) that the atom contains. Electron configuration The distribution of electrons among the orbitals of an atom. Isotopes Are an atom of the same element with same number of protons but different number of neutrons. Mass number Is the number of protons plus number of neutrons. Number of neutron Is the mass number minus atomic number. Periodic table Is a chart of all the known elements in order of increasing atomic number. Periodic trend Is a property that changes as you move across a period or down a group of the periodic table. Relative isotopic mass Is the mass of an atom of the isotope relative to the mass of an atom. 7  GR 11 CHEM M2 CHEMICAL AND METALLIC BONDING 11.2.1 Atomic Structure atom nucleus electrons protons neutrons negative charge positive neutral charge charge Inside the atom This topic explains the structure of matter. Matter is composed of tiny particles called atom. An atom is the smallest particle of an element. Atoms of different elements may also combine into systems called molecules, which are the smallest modules of chemical compounds. These are also considered as the ultimate building blocks of matter. What are atoms made of? What makes one type of atom different from another? A careful study of the atom shows that it has a small, but dense core called the nucleus. The nucleus is composed of protons the positively charged particle and the neutrons, the particle with no charge. Around the nucleus is the electron, the negatively charged particle. The atomic structure Different Atomic Models 8  GR 11 CHEM M2 CHEMICAL AND METALLIC BONDING The table shows the charge and mass of the particles in an atom. Particle Charge Mass Discoverer Proton 1+ 1 Eugene Goldstein Neutron 0 1 James Chadwick Electron 1- 0 (almost) J.J Thomson Nucleus Ernest Rutherford I am the Proton. I am pretty large with a positive charge. My friends and I in the nucleus we huddle. It is nice and cosy with neutrons to cuddle. I am the Electron. I am pretty quick with a negative charge and fly around the nucleus at a fair old lick. The protons and I, we tend to attract. I am the Neutron. I am pretty heavy, fat lazy and take things steady. You can call me cheap, no charge at all, a neutral ball. The atom is the element helium (He)..Its position in the periodic table is second, and it has the atomic number 2. Each element on the periodic table has a different atomic number. The atomic number represents the number of protons an of a particular elements contains in its nucleus. The number of protons equals the number of electrons. Position of atomic mass and atomic The total number of protons in a given atom number in Periodic Table determines the atomic number of an element. The atomic number is the number of protons (positively charged elementary particles) in the nucleus of one of its atoms. If the atom is electrically neutral, the same number of electrons is present, since the number of protons is equal to the number of electrons. The atomic mass or mass number is the sum of an atom's protons and neutrons that are always expressed in whole numbers. 9  GR 11 CHEM M2 CHEMICAL AND METALLIC BONDING For example, 126 C indicates a carbon atom Protons + Neutrons = Atomic Mass of atomic mass 12 and atomic number 6, Number the difference being equal to the Symbol number of neutrons in the nucleus. This means for 126 C, there are 6 protons and 6 Number of Protons = Atomic Number neutrons. It follows that it has 6 electrons, too. (In other presentations of The Modern Periodic Table, the superscript is the atomic number and the subscript is the atomic mass. The atomic number is always less than the atomic mass). Number of neutrons + Number of protons = Mass number Atomic number = number of protons (also number of electrons) Mass number = number of protons plus number of neutrons Number of neutrons = mass number minus atomic number Now, check what you have just learnt by trying out the learning activity below! Learning Activity 1 30 minutes Answer the following questions: 1. What are the sub- particles found inside the atom? i. __________ ii. __________ iii. __________ 10  GR 11 CHEM M2 CHEMICAL AND METALLIC BONDING 2. Complete the table (by showing their masses and charge.) Sub – atomic particles charge Mass ( atomic mass module) Proton 0 1 0 ( almost) 3. Give the number of protons, electrons and neutrons in the atom below: a) N number of protons __________ number of electrons __________ number of neutrons __________ b) K number of protons __________ number of electrons __________ number of neutrons __________ c) Ne number of protons __________ number of electrons __________ number of neutrons __________ Thank you for completing your learning activity 1. Check your work. Answers are at the end of this module. Relative Atomic Mass Each type of atoms has a different mass. However, the mass of an atom is too small to measure. So we compare their masses on a scale which gives the lightest element of all, hydrogen, a mass of 1. This gives us the number called the relative atomic mass. (R.A.M). Sometimes given the symbol Ar. Let us look, more closely at the hydrogen atom. Hydrogen’s atomic number is 1. Its mass number is also 1. This means that hydrogen atom has 1 proton, 1 electron, but no neutrons. You can see why it is so light! You might think that there is no point having relative atomic mass and mass number. Both seem to tell us how heavy atom is. 11  GR 11 CHEM M2 CHEMICAL AND METALLIC BONDING What are isotopes? Isotopes are an atom of the same element with same number of protons but different number of neutrons. Stable atoms Un-stable atom Carbon 12 Carbon 13 Carbon 14 6 protons 6 protons 6 protons 6 neutrons 7 neutrons 8 neutrons Why carbon-14 is unstable? If an atom has too many neutrons in its nucleus, it is unstable and will change into a stable form. To date a sample, scientists calculate how much time would be required for the unstable atoms in the sample to change into a stable form. For example, most carbon atoms are stable because they have only six or seven neutrons in their nuclei (carbon-12 and carbon-13, above). But some carbon atoms have too many neutrons and are unstable (carbon-14) Relative isotopic mass is the mass of an atom of the isotope relative to the mass of an atom. Relative Isotopic Mass =mass of one atom of that isotope relative to the mass of one atom of 12C = 12 units exactly. Most elements, like chlorine, are a mixture of isotopes. Details of isotopes of some common elements are shown in the table below. Element Isotopes Relative isotopic mass Abundance (%) 1 Hydrogen H 1.008 99.986 2 H 2.014 0.014 3 H 3.016 0.0001 12 Carbon C 12 98.888 13 C 13.003 1.112 14 C 14.003 Approx.10-10 35 Chlorine Cl 34.969 75.0 37 Cl 36.966 25. Isotopic compositions of some elements 12  GR 11 CHEM M2 CHEMICAL AND METALLIC BONDING Relative atomic masses of elements can be obtained using an instrument called a mass spectrometer. This separates the individual isotopes in a sample of element being measured and determines the mass of each isotope relative and the relative abundance of the isotopes. This information presented graphically is called mass spectrum. A mass spectrometer consists of an ion source, an analyser and a detector. Particles must be ionized so they can be accelerated and deflected. Mass spectrometry has been described as the smallest scale in the world, not because of the mass spectrometre’s size but because of the size of what it weighs the molecules. For example: Chlorine has two isotopes 37Cl with the the abundance of 25% and 35 Cl with 75% abundance. Using this information provided by a mass spectrum we can now calculate the relative atomic mass of chlorine. The total mass of 100 atoms of chlorine: isotope 1 x abundance (%) + isotope 2 x abundance (%) = 100 35 x 75% + 37 x 25% = = 35.5 100 Relative atomic mass of chlorine is 35.5 Now, check what you have just learnt by trying out the learning activity below! Learning Activity 2 30 minutes Answer the following questions: 1. Define the following: i. Isotope _______________________________________________ ii. Mass spectrometer _______________________________________________ 13  GR 11 CHEM M2 CHEMICAL AND METALLIC BONDING 2. Using the different isotopes and abundance, calculate the relative atomic mass of the following: 63 i. Cu with 69%, 65Cu with 31%. 16 ii. O with 99.79%, 17O with 0.04%, 18O with 0.20%. Thank you for completing your learning activity 2. Check your work. Answers are at the end of this module. Electrons in Orbit Electron shells The electrons in the atom are arranged in shells around the nucleus.  The shells are sometimes called orbital’s or energy levels.  The first shell can hold just 2 electrons.  The second shells can hold up to 8 electrons.  The third shell can also hold 8 electrons. th 4 shell holds 32 electrons rd 3 shell holds 18 electrons nd 2 shell holds 8 electrons st 1 shell holds 2 electrons Electron Shells 14  GR 11 CHEM M2 CHEMICAL AND METALLIC BONDING 1. The distribution of electrons among the orbitals of an atom is called electron configuration. 2. The s, p, d, and f are called sublevels; they are smaller "subdivisions" of energy within the primary levels. 3. You refer to different energy levels using a number for the primary level plus a letter for the sublevel; for example, you might speak of an electron in a "3p" state or orbital. Each primary level has one more sublevel than the one below: the first primary level has only s orbitals; the second has s and p, the third s, p, and d. s – sharp 2 electrons to fill p – principal 6 electrons to fill d – diffuse 10 electrons to fill f – fundamental 14 electrons to fill Total number of electrons in an energy level can be found by the formula: number of electrons = 2n2 Where n is the number of energy level 1st = 2 2nd = 8 = (2+6) 3rd = 18 = (2 +2+ 6 = 10) 4th = 32 = (2 + 6 + 10 + 14) Do you know that after Mendeleev’s time, scientist discovered what you already know. An atom consist of a positively charge nucleus, made of protons and electrons moving around it. This is shown by electron configuration. Electron configuration? I am not sure if I understand what that means. How do I go about it? Does it have something to do with the s, p, d, and f? Yes, electron configuration shows how the electrons are arranged in the selected element. The chart below explains how the electrons organise themselves. 15  GR 11 CHEM M2 CHEMICAL AND METALLIC BONDING Chart of organised electrons It say that groups I and II belong to s block, group III to VIII belong to the p block, transition metals to the d block and the lanthanides and actinides to the f block. But, how will I do it? Can you give me a pattern to make it easier and faster? Very easy! Just follow the arrows. 4f 5f 3d 4d 5d 6d 2p 3p 4p 5p 6p 7p 1s 2s 3s 4s 5s 6s 7s Electronic configuration 16  GR 11 CHEM M2 CHEMICAL AND METALLIC BONDING Below are some examples of electron configuration. Now I got !it! Elements Symbol Atomic Number Electron Configuration Period Group 1 1.Hydrogen H 1 1s 1 IA 2 1 2.Lithium Li 3 1s 2s 2 IA 2 2 3.Berylium Be 4 1s 2s 2 IIA 2 2 2 4.Carbon C 6 1s 2s 2p 2 IVA 2 2 3 5.Nitrogen N 7 1s 2s 2p 2 VA 2 2 6 2 1 6.Aluminum Al 13 1s 2s 2p 3s 3p 3 IIIA 2 2 6 2 4 7.Sulphur S 16 1s 2s 2p 3s 3p 3 VIA 2 2 6 2 6 1 8.Potassium K 19 1s 2s 2p 3s 3p 4s 4 IA 2 2 6 2 6 2 10 5 9.Bromine Br 35 1s 2s 2p 3s 3p 4s 3d 4p 4 VIIA Analysis of the Table Take note of the coefficient of the last energy level. Notice also the exponent or the number on the superscript of the letter of the last energy level. The coefficient represents the series or the period of the element and the superscript or the exponent represents the number of electrons in the outermost energy level or simply the valence electrons. It is also the Family or the Group Number of the element. Now, check what you have just learnt by trying out the learning activity below! Learning Activity 3 30 minutes Answer the following questions: 1. Define electron configuration. _______________________________________________________________________ _______________________________________________________________________ 2. Draw the electron configuration of the following using the s, p, d and f. a) Na ________________________________________________________ b) Ca ________________________________________________________ c) Cl ________________________________________________________ d) Zn ________________________________________________________ 17  GR 11 CHEM M2 CHEMICAL AND METALLIC BONDING e) F ________________________________________________________ f) Al ________________________________________________________ Thank you for completing your learning activity 3. Check your work. Answers are at the end of this module. 12.2.2 Periodic Table The Development of Periodic Table  400 BC Democritus suggest that all things are made of particles.  1805 John Dalton’s atomic theory. Atoms of the same element are alike. They combine to make compounds.  1909 Ernest Rutherford discover the proton.  1911 Ernest Rutherford discover the nucleus.  1913 Neil’s Bohr suggests those electrons are found in shells around the nucleus.  1932 James Chadwick proves that neutrons exist. The early years of the 19th century witnessed a rapid development in chemistry. The art of distinguishing similarities and differences among atoms prompted scientists to devise a way of arranging the elements. Relationships were discerned more readily among the compounds than among the elements. Thus, the classification of elements lagged many years behind the classification of compounds. In fact, no general agreement had been reached among chemists as to the classification of elements for nearly half a century after the systems of classification of compounds had been established. It was in 1817 when Johann Wolfgang Döbereiner showed that the atomic weight of strontium lies midway between those of calcium and barium. Some years later he showed that other such “triads” exist (chlorine, bromine, and iodine [halogens] and lithium, sodium, and potassium [alkali metals]). He also showed that similar relationships extended further than the triads of elements, fluorine being added to the halogens, and magnesium to alkaline-earth metals. Oxygen, sulfur, selenium, and tellurium were classed as one family, and nitrogen, phosphorus, arsenic, antimony, and bismuth as another family of elements. 18  GR 11 CHEM M2 CHEMICAL AND METALLIC BONDING Another way of classifying the elements was later proposed by John Alexander Reina Newlands in 1864. He proposed that elements be classified in the order of increasing atomic weights, the elements being assigned ordinal numbers from one upward and divided into seven groups, with each group having properties closely related to the first seven of the elements then known: hydrogen, lithium, beryllium, boron, carbon, nitrogen, and oxygen. Mendeleev’s version of the periodic table The rows 1 to 7 are called periods. The columns I on the left to 0 on the right are known as groups. Elements with similar properties fall into vertical columns (groups) and horizontal rows (periods), which form the table. Elements within the groups have similar valences. Mendeleev left spaces in his table for elements not yet discovered. He also predicted what properties these undiscovered elements would have. Between 1875 and 1886, the elements gallium, scandium and germanium were discovered. They all fitted into the positions predicted by Mendeleev. As a result, the periodic law gained universal acceptance. The elements in the same row have something in common. All of the elements in a period have the same number of electron shells. Both elements in the top row (the first period) have one shell for their electrons. All elements in the second period have two electron shells. The number of shells increases as you go down the table.The columns in the table is called Groups. The elements in a group have the same number of electrons in their outer shell. So, all elements in Group I have one electron in their outer shells. The elements in Group II have two electrons in the outer shell. 19  GR 11 CHEM M2 CHEMICAL AND METALLIC BONDING 20 GR 11 CHEM M2 CHEMICAL AND METALLIC BONDING 21  GR 11 CHEM M2 CHEMICAL AND METALLIC BONDING Study the terms below for you to be familiar with the modern periodic table:  Periodic table is a chart of all the known elements in order of increasing atomic number. The table puts elements into groups with similar characteristics, allowing us to recognize trends over the whole array of elements.  Atom is the smallest module of a substance that still has all the properties of that substance. In most cases, an atom consists of protons, neutrons, and electrons. The protons and neutrons are found in the center of the atom, called the atomic nucleus and the electrons orbit or circle around the center of the nucleus in paths called orbitals.  Atomic number of an atom is equal to the number of protons that the atom contains. Atoms can have differing numbers of neutrons and electrons while still retaining the original characteristic properties of that atom. However, if an atom gains or loses a proton, in essence, it changes its atomic number and becomes an entirely new atom with new characteristics.  Atomic mass of an atom is a measure of how much mass an atom has. The atomic mass is calculated by adding the number of protons and neutrons together. Atomic masses are not listed as whole numbers on the periodic table because atoms can come in forms with different amounts of neutrons. The Elements in the Periodic Table How are elements named? Chemists have developed a unique system of symbols and notation designed to simplify the writing of chemical symbols, formula, and reactions. This system also shows the mathematical relations of atoms and reacting chemicals, the way atoms are put together to form complex molecules. Elements, in most cases he was able to use the first letter of the name of the element as its symbol: O stood for oxygen, C for carbon, H for hydrogen, and so on. Two letters are used to distinguish between elements that have the same initial letter: N for nitrogen, Ne for neon, and Ni for nickel. Sometimes the symbol is derived from the Latin name of the element, example gold (aurum) is Au, iron (ferrum) is Fe, and lead (plumbum) is Pb. Whenever two letters are used for an element, the first letter is capitalized but the second is not. Thus, the element cobalt, Co, is distinguished from the compound carbon monoxide, CO Some Elements Familiar Place or Name Symbol of Element Californium California Cf Einsteinium Albert Einstein Es Nobelium Alfred Nobel (Nobel Prize) No Neptunium Neptune Ne Plutonium Pluto Pu Americium America Am Berkelium Berkeley, California Bk 22  GR 11 CHEM M2 CHEMICAL AND METALLIC BONDING Now, check what you have just learnt by trying out the learning activity below! Learning Activity 4 30 minutes Answer the following questions: 1. Define the following terms: i. Atom ____________________________________________________ ii. Atomic mass ____________________________________________________ iii. Atomic number ____________________________________________________ 2. In what year the neutron was discovered? __________________________________ 3. Who discovered the electron? __________________________________ Thank you for completing your learning activity 4. Check your work. Answers are at the end of this module. Periodic Table Variations The Periodic Table and the Elements The periodic table is composed of 7 (rows) or periods and 8 major groups or (columns). Elements in a group have similar properties particularly those elements in groups: Group I (The Alkali metals) Group II (the Alkaline earth metals) Group VII the (Halogens) and Group VIII the (Noble gases). 1. The elements are given symbols devised by John Jacob Berzelius. An element is named after its discoverer, place of discovery, first letter of the name of the element, first and the second letter for those having the same first letter and some are after their Latin names. The elements are grouped into Group A and B Group by the INTERNATIONAL UNION OF PURE AND APPLIED CHEMISTRY (IUPAC) 2. Elements in the Periodic Table are also grouped according to metals, non-metals and metalloids. Metals are lustrous, malleable and ductile. They are good conductors of heat. Metals are found on the left side of the periodic table. Non-metals have a many set of properties. They are found on the upper right side of the periodic table. Metalloids or semimetals possess the properties of both the metals and the non- metals. 23  GR 11 CHEM M2 CHEMICAL AND METALLIC BONDING Periodic Trends A periodic trend is a property that changes as you move across a period or down a group of the periodic table. The table below shows the example of some elements. Metals Symbol Non- metals Symbol Metalloids Symbol Sodium Na Carbon C Silicon Si Copper Cu Oxygen O Arsenic As Calcium Ca Fluorine F Antimony Sb Magnesium Mg Chlorine Cl Germanium Ge The Periodic Trends The following are the trends of elements in the periodic table. 1. Atomic radius increases as you move down a group and decreases as you move across. 2. Ionization energy is the energy needed to remove an electron to form a positive ion. 3. Electron affinity is the energy change that occurs when an atom gains an electron to form a negative ion. 4. An element’s electronegativity reflects its attraction for electrons in a chemical bond. 5. The s, p, d, and f are called sublevels; they are smaller "subdivisions" of energy within the primary levels. You refer to different energy levels using a number for the primary level plus a letter for the sublevel; for example, you might speak of an electron in a "3p" state or orbital. Each primary level has one more sublevel than the one below, the first primary level has only s. Orbitals; the second has s and p, the third s, p, and d, and so forth. 24  GR 11 CHEM M2 CHEMICAL AND METALLIC BONDING Pattern and trends in the Periodic Table This lesson will focus on the arrangement of the elements in the periodic table based on their properties. Read the comic strips below. You will need your own periodic table for this activity. How are elements arranged in the periodic table? Elements are arranged from the lightest to heaviest. Ah ok! What you said was actually a very important insight. The periodic table is full of repeating patterns. Take atomic size, for example, atoms get bigger as you move down to the right across a row or a period. Study the table below. What does it show? Compare it to your Periodic table. 25  GR 11 CHEM M2 CHEMICAL AND METALLIC BONDING Now, I know! How about atomic size and structure? That is another thing. We will talk about that when we go to the next lesson. For the mean time, let us summarize what you have learned in this lesson. What about ionization energy? Electronegativity? Electron affinity? Ok, that is a nice question! First, I would like you to know the meaning of these terms. Ionization energy is an energy required to remove the outer electron from an isolated atom. Electron affinity is the releases when a neutral atom gains an extra electron to form negatively charged ion. Electronegativity is the electron attracting ability to an atom. For horizontal arrangement of elements, there are two distinct trends in the atomic radius of the elements in the periodic table. 1. Atoms get larger going down a group (vertical arrangement or column). 2. Atoms get smaller moving from left to right across each period. Example of electronegativity values of some of the lighter elements. Group I II III IV V VI VII Li Be B C N O F 1.0 1.6 2.0 2.5 3.0 3.5 4.0 Na Mg Al Si P S Cl 0.9 1.3 1.6 1.9 2.2 2.6 3.2 The atomic radius is affected by the ionization energy, electronegativity and electron affinity. As you go across from left to right, ionization energy, electro negativity and electron affinity increase, thus the atomic radius decreases. From top to bottom, ionization energy, electronegativity and electron affinity decreases, thus the atomic radius increases. 26  GR 11 CHEM M2 CHEMICAL AND METALLIC BONDING The table below shows the example of position of electron configuration. Elements Electron configuration Group number Period number Sodium, Na 11- 2,8,1 I 3 Iron, Fe 13 – 2,8,3 III 2 Oxygen, O 8 - 2,6 VI 1 Sulphur,S 16 – 2,8,6 IV 3 Silver, Ag 47 – 2,8,18,18,1 I 5 Iodine, I 53- 2,8,18,18,7 VII 5 Radon, Rn 86 – 2,8,18,32,18,8 VIII 6 Now, check what you have just learnt by trying out the learning activity below! Learning Activity 5 30 minutes Answer the following questions: 1. Define the following terms: i. Metalloid ___________________________________________________ ii. Ionization energy ____________________________________________________ III. Electron affinity ____________________________________________________ iv. Electronegativity ____________________________________________________ 2. Give the two distinct trends in the atomic radius of the elements in the periodic table. I. __________________________________________________________________ ii. __________________________________________________________________ 3. How are elements arranged in the periodic table? _______________________________________________________________________ Thank you for completing your learning activity 5. Check your work. Answers are at the end of this module. 27  GR 11 CHEM M2 CHEMICAL AND METALLIC BONDING The group These elements are organized using the Periodic Table. A periodic table is a classification and tabulation of the elements in the order of their atomic numbers and atomic masses that show the elements' chemical and physical properties. How are elements grouped? Take note of the colour-coding in the periodic table. Elements are grouped according to metals, nonmetals, and metalloids. Metals are solid, malleable, ductile and good conductors of heat. They also possess luster. The only liquid metal is mercury; (Hg).Nonmetals can be solids, liquids or gases. The only liquid nonmetal is bromine, (Br). In-between metals and nonmetals that lie along either side of the zigzag line of the periodic table are the metalloids. Some of these elements like boron (B) and silicon (Si) are used as semiconductors. How are elements classified? Elements are classified based on their positions or locations in the periodic table. Group I The Alkali Metals Group 1 elements are soft silvery metals. They react strongly with water. The further down the group you go, the more violent this reaction is. These alkali metals are usually stored under oil to protect them from moisture and oxygen. They all have one electron in their outer shells. In a chemical reaction an alkali metal atom loses this single electron. It achieves the stable electron structure of the noble gases. Group II The Alkaline Earth Metals This group consists of all metals that occur naturally in compound form. They are obtained from mineral ores and form alkaline solutions. These are less reactive than alkali metals. Group III The Aluminum Group The elements in this group are fairly reactive. The group is composed of four metals and one metalloid which is boron. Group IV The Carbon Group This group is composed of elements having varied properties because their metallic property increases from top to bottom meaning the top line, which is carbon, is a nonmetal while silicon and germanium are metalloids, and tin and lead are metals. Group V The Nitrogen Group Like the elements in group IV A, this group also consists of metals, nonmetal and metalloids. 28  GR 11 CHEM M2 CHEMICAL AND METALLIC BONDING Group VI The Oxygen Group This group is called the oxygen group since oxygen is the top line element. It is composed of three nonmetals, namely: oxygen, sulfur and selenium, one metalloid,(tellurium) and one metal (polonium) Group VII The Halogens This group is composed of entirely non-metals. The term halogens come from the Greek word (hals) which means salt and genes which means forming. Halogens group are called (salt former). Group VIII The Noble Gases This group is composed of stable gases otherwise known as the non- reactive or inert elements. The transition elements The elements in the middle of the table are called transition elements. They are all metals and so they are also called transition metals. A group was devised by the International Union of Applied and Pure Chemistry (IUPAC) to eliminate confusion. The table below shows the example of trends across a period in the periodic table. (Period 3) Group I II III IV V VI VII 0 Element Sodium Magnesium Aluminium Silicon Phosphorus Sulphur Chlorine Argon Valence electrons 1 2 3 4 5 6 7 8 Element is a….. Metal Metal Metal Metal Non-metal Non- Non- Non- -loid metal metal metal Reactivity high low high Unre- active Melting point/°C 98 649 660 1410 590 119 -101 -189 Boiling point/°C 883 1107 2467 2355 Ignites 445 -35 -186 Oxide is…. basic amphoteric acidic - Typical compound NaCl MgCl2 AlCl3 SiCl4 PH3 H2S HCl - Valency shown in 1 2 3 4 3 2 1 - that compound 29  GR 11 CHEM M2 CHEMICAL AND METALLIC BONDING Now, check what you have just learnt by trying out the learning activity below! Learning Activity 6 30 minutes Answer the following questions: 1. What is the other name for the group I elements? ___________________________ 2. Explain why the noble gases are unreactive. _______________________________________________________________________ 3. Draw the atomic structure of the following elements and identify what group and period they belong? a) Zn Group______ period ______ b) Al Group______ period ______ c) F Group______ period ______ Thank you for completing your learning activity 6. Check your work. Answers are at the end of this module. 30  GR 11 CHEM M2 CHEMICAL AND METALLIC BONDING 11.2.3 Bonding and Structure Chemical bonding You have read about the electronic configuration of atoms of different elements and variation in the periodic properties of elements. Chemical bonds which join the atoms together will give various types of substances. The discussion would also highlight how these bonds are formed. The properties of substances depend on the nature of bonds present between their atoms. In this lesson you will learn that sodium chloride, the common salt and washing soda dissolve in water whereas methane gas or napthalene do not. This is because the type of bonds is present between them are different. In addition to the difference in solubility, these two types of compounds differ in other properties. Why do atoms combine? The answer to this question is hidden in the electronic configurations of the noble gases. It was found that noble gases namely: helium, neon, argon, krypton, xenon and radon did not react with other elements to form compounds. They are not reactive. They were also called inert gases due to their non-reactive nature. Thus, it was thought that these noble gases lacked reactivity because of their stable electronic configuration. When we write the electronic configurations of the noble gases (see table below), we find that all of them have 8 electrons in their outermost shell except helium. Name Symbol Atomic number Electron Number of electrons configuration in the outermost shell Helium He 2 2 2 Neon Ne 10 2,8 8 Argon Ar 18 2,8,8 8 Krypton Kr 36 2,8,18,8 8 Xenon Xe 54 2,8,18,18,8 8 Radon Ra 86 2,8,18,32,18,8 8 Electronic configuration of noble gases Atoms having 8 electrons in their outermost shell are very stable. They did not form compounds. It was also observed that other atoms such as hydrogen, sodium, chlorine do not have 8 electrons in their outermost shell undergo chemical reactions. They can be stable by combining with each other and attain the above configurations of noble gases. Example, 8 electrons (or 2 electrons in case of helium) are in their outermost shells. Thus, atoms tend to attain a configuration in which they have 8 electrons in their outermost shells. 31  GR 11 CHEM M2 CHEMICAL AND METALLIC BONDING This is the basic cause of chemical bonding. This attainment of eight electrons for stable structure is called the octet rule. The octet rule explains the chemical bonding in many compounds. Atoms are held together in compounds by the forces of attraction which result information of chemical bonds. The formation of chemical bonds results in the lowering of energy which is less than the energy of the individual atoms. The resulting compound is lower in energy as compared to sum of energies of the reacting atom/molecule and hence is more stable. Thus, stability of the compound formed is an important factor in the formation of chemical bonds. Types of chemical bonds 1. The Ionic bond The chemical bond formed by transfer of electron from a metal to a non- metal is known as ionic or electrovalent bond. For example, when sodium metal and chlorine gas are brought into contact, they react violently and we obtain sodium chloride. This reaction is shown below: Chloride ion Sodium Sodiumion ion Reaction of sodium chloride ions 2Na(s) + Cl2 (g) → 2NaCl(s) The bonding in sodium chloride can be understood as follows: Sodium (Na) has the atomic number 11 and we can write its electronic configuration as 2,8 and 1. It has one electron in its outermost (M) shell. If it loses this electron, it is left with 10 electrons and becomes positively charged. Such a positively charged ion is called a cation. The cation in this case is called sodium ion, Na+. Na (s) + Cl (g) Na+ Cl- NaCl (S) 2, 8, 1 2, 8, 7 2, 8 2, 8, 8 Proton transfer 32  GR 11 CHEM M2 CHEMICAL AND METALLIC BONDING Na atom. It has 1 Cl atom. It has 7 electrons electron in its outer shell in its outer shell The atom of sodium and chlorine Sodium gives its outer electron to chlorine The ion of sodium and chlorine. Remember that all atoms are neutral. They have an equal number of positive protons and negative electrons. So the charges cancel out, the electrons and protons in both atoms no longer balance. Let’s add up the charges: Sodium 10 electrons =10 – Chlorine 18 electrons = 18- + 11 Protons = 11 17 protons = 17 + 1+ 1- The atoms, which we now call ions, become charged: Na+ and Cl- transfer Na= 2,8,1 Na= 2,8,7 Na= 2,8 Na= 2,8,8 The ionic compound of sodium chloride. 33  GR 11 CHEM M2 CHEMICAL AND METALLIC BONDING Sodium chloride Compound of sodium chloride. Another example of ionic bonding is between Magnesium and Chlorine atom. We know that in the first example between sodium and chlorine the atoms satisfy each other – one to one. So the formula of Sodium chloride is NaCl. How about Magnesium? We know that it has 2 electrons in the outer shell. What do you think will happen? Look at the diagram below: Mg2+ + 2Cl - MgCl2 Cl- ion [2, 8, 8] Mg2+ ion [2, 8, Cl- ion [2, 8, 8] 8] You can see now that each magnesium atom can `satisfy’ 2 chlorine atoms. 34  GR 11 CHEM M2 CHEMICAL AND METALLIC BONDING Properties of ionic compounds Since the ionic compounds contain ions (cations and anions) which are held together by the strong electrostatic forces of attraction, they show the following general characteristic properties: (a) Physical State Ionic compounds are crystalline solids. In the crystal, the ions are arranged in a regular pattern. The ionic compounds are hard and brittle in nature. (b) Melting and boiling points Ionic compounds have high melting and boiling points. The melting point of sodium chloride is 1074 K (801°C) and its boiling point is 1686K (1413°C). The melting and boiling points of ionic compounds are high because of the strong electrostatic forces of attraction present between the ions. Thus, it requires a lot of thermal energy to overcome these forces of attraction. The thermal energy given to the ionic compounds is used to overcome the strong force of attractions present in the cations and anions in an ionic crystal. Remember that the crystal has a three dimensional regular arrangement of cations and anions which is called crystal lattice. On heating, the breaking of this crystal lattice leads to the molten state of the ionic compound in which the cations and anions are free to move. (c) Electrical Conductivity Ionic compounds conduct electricity in their molten state and in aqueous solutions. Since ions are free to move in the molten state, they can carry current from one electrode to another in a cell. Thus, ions can conduct electricity in molten state. However, in solid state, such a movement of ions is not possible as they occupy fixed positions in the crystal lattice. Hence in solid state, ionic compounds do not conduct electricity. In aqueous solution, water is used as a solvent to dissolve ionic compounds. It weakens the electrostatic forces of attraction present among the ions. When these forces are weakened, the ions become free to move. 2. The Covalent Bond In this section, we will study about another kind of bonding called covalent bonding. Covalent bonding is helpful in understanding the formation of molecules. In the previous lesson you studied about molecules having similar atoms such as hydrogen (H2), chlorine (Cl2), oxygen (O2), and nitrogen (N2). Molecules of elements whereas those containing different atom like hydrochloric acid HCl, nitric acid NH3, methane CH4, carbon dioxide CO2 are molecules of compounds. 35  GR 11 CHEM M2 CHEMICAL AND METALLIC BONDING Let us now see how these molecules are formed. Let us consider the formation of hydrogen molecule (H2). The hydrogen atom has one electron. It can attain the electronic configuration of the noble gas helium by sharing one electron of another hydrogen atom. When the two hydrogen atoms come closer, there is an attraction between the electrons of one atom and the proton of another and there are repulsions between the electrons as well as the protons of the two hydrogen atoms. In the beginning, covalent bond forms by sharing electrons between non- metals. Two non- metals atoms can both gain electrons by sharing. If their outer shells overlap, they share some of each other’s electrons. This can `satisfy’ both atoms. Let us look at the smallest hydrocarbon, Methane (CH4). Carbon atom has 4 electrons in its Hydrogen has just 1 electron. If it can outer shell. It needs to get full outer gain 1 more electron, it will fill its shell. shell. Atoms of carbon and hydrogen. Count the electrons in the outer shell of each carbon and hydrogen atom in methane. Are they full? Can you see that the carbon now has 8 electrons in its outer shell? And hydrogen has 2? It means that all atoms of hydrogen and carbon are stable. 36  GR 11 CHEM M2 CHEMICAL AND METALLIC BONDING Let us look at another example of covalent bonding. Chlorine gas does not exist as single atoms. Remember that a chlorine atom has 7 electrons in its outer shell. It needs 1 more electron to fill it. Chlorine atom Chlorine atom Chlorine molecule Covalent bond Ways to show the covalent bond between Cl2. The right – hand is a `dot and cross’ diagram. (showing the outer electrons only.) Like many gases, it is a diatomic. Two chlorine atoms bond together to make a Cl2 molecules. Look at the diagram below of Cl2 molecules: Chlorine molecule 37  GR 11 CHEM M2 CHEMICAL AND METALLIC BONDING Double bond Do you recall the molecules ethene? Its formula is C2H4. We said that its carbon atoms joined by a double bond. Let us look at the diagram below: H H C=C H H Ethane has a double covalent bond between its carbon atoms Oxygen is another molecule contains a double bond. Triple bond Another type of covalent bond is the triple bond. Can you think of elements that form a triple bond? Example: nitrogen molecule Nitrogen molecule showing the outer shell electrons. 38  GR 11 CHEM M2 CHEMICAL AND METALLIC BONDING Properties of covalent substances The covalent compounds consist of molecules which are electrically neutral in nature. The forces of attraction present between the molecules are less strong as compared to the forces present in ionic compounds. Therefore, the properties of the covalent compounds are different from those of the ionic compounds. The characteristic properties of covalent compounds are given below: a. Physical state Because of the weak forces of attraction present between discrete molecules, called intermolecular forces, the covalent compounds exist as a gas or a liquid or a solid. For example O2, N2, CO2 are gases; water and CCl4 are liquids and iodine is a solid. b. Melting and boiling points As the forces of attraction between the molecules are weak in nature, a small amount of energy is sufficient to overcome them. Hence, the melting points and boiling points of covalent compounds are lower than those of ionic compounds. For example, melting point of naphthalene which is a covalent compound is 353 K (80°C).Similarly, the boiling point of carbon tetrachloride which is another covalent liquid compound is 350 K (77°C). c. Electrical conductivity The covalent compounds contain neutral molecules and do not have charged species such as ions or electrons which can carry charge. Therefore, these compounds do not conduct electricity and are called poor conductors of electricity. Giant covalent structures The great variety of life on Earth depends on carbon’s ability to form covalent bonds with itself. As the element, carbon atoms can bond to millions of other carbon atoms in both diamond and graphite, the allotropes of carbon. Allotrope is the same element with different physical properties. The structures, properties and uses of diamond and graphite. Diamond Graphite It occurs naturally in free state. It occurs naturally and manufactured artificially. It is the hardest natural substance known. It is soft and greasy to touch. It has high relative density (3.5). Its relative density is 2.3. It has transparent and has refractive. It is black in colour and opaque. It is non-conductor of heat and electricity. It is a good conductor of heat and electricity. It burns in air at 900oC to give carbon It burns in air at 700-800oC to give carbon dioxide. dioxide. It occurs as octahedral crystals. It occurs as hexagonal crystals. It is insoluble in all substance. It is insoluble in all ordinary substance. 39  GR 11 CHEM M2 CHEMICAL AND METALLIC BONDING Carbon in the form of diamonds Diamond’s hardness makes it very useful material. It is a form from carbon atoms only. Uses of diamonds: (i) Diamonds are valuable gemstones. Larger and purer the diamond, the more valuable it is. (ii) Diamonds are used in jewellery such as rings, earrings, pendants, bangles or necklaces. (iii) Smaller pieces of diamonds are used for cutting glass and drilling rocks. (iv) Only a diamond can cut another diamond. Diamond dust is used for polishing diamonds and precious stones. (v) In the future, diamonds may be used for surgical tools, medical devices, and prosthethic human joints. Carbon in the form of graphite Another form of carbon is graphite. If you touch a lump of graphite, it feels smooth and slippery. One use of graphite is the pencil leads. If you use pencil to draw, as you move it across your paper it flakes off, leaving a trail of carbon atoms. graphite 40  GR 11 CHEM M2 CHEMICAL AND METALLIC BONDING Some other uses of graphite: (i) Graphite being smooth and slippery, is used in making lubricants for use in machinery, motorcar engines and even bicycle chains. (ii) Graphite being chemically unreactive and a conductor of electricity, is used in making electrodes for use in electrolysis and in dry cells. (iii) Due to its very high melting point, graphite is used as a heat insulator. It is used to coat the nose of a space shuttle. 3. Metallic bonding Think of some of the things around your home that are made of metal. Did you include all the wiring, any radiators, your hot – water tank, or your cutlery and pans? Different kinds of metals Do you know which metals these things are made from? Which properties make metals good for these uses? In the last topic you have learnt ionic and covalent bonding. The atoms in a metal are held together in a different way. Do you remember all the properties of metals? Any ideas we have about the bonding and structure of metals must be able to explain their properties. Properties of metals  Have high melting and boiling points.  Conduct electricity and heat.  Are hard and dense.  Can be hammered into shapes ( they are malleable).  Can be drawn out into wires (they are ductile). 41  GR 11 CHEM M2 CHEMICAL AND METALLIC BONDING We believe that metal atoms (or ions) are held together by a sea of electrons. Look at the diagram below: Metal ions in their sea of electrons. Each metal atom gives up one or more of its electrons into the `sea’ or `cloud’ of electrons. The electrons can drift about in the metal. These free electrons explain how electricity can pass through solid metals. What happens when one end of the metal is made up of positive and the other end negative? The diagram below represents the movement of electrons. Electrons move towards the positive charge. These free electrons can also transfer heat through metals quickly. Structure of the metals As you know, most metals are dense. This suggests that their atoms must be packed closely together. They also have high melting points. And their atoms are arranged in giant structures. Metals are giant structures of atoms held together by metallic bonds. Giant implies that large but variable numbers of atoms are involved - depending on the size of the bit of metal. Metals form giant structures in which electrons in the outer shells of the metal atoms are free to move. The metallic bond is the force of attractions between these free electrons and metal ions. 42  GR 11 CHEM M2 CHEMICAL AND METALLIC BONDING Metallic bonds are strong, so metals can maintain a regular structure and usually have high melting and boiling points. Metals are good conductors of electricity. Giant structure of metal. Now, check what you have just learnt by trying out the learning activity below! Learning Activity 7 40 minutes Answer the following questions: 1. Name two ions present in sodium chloride. I. _____________ ii _____________ 2. How many shells are present in Na+ ion? _____________ 3. What is the number of electrons present in Cl– ion? _____________ 4. How are covalent bonds formed? ______________________________________________________________________ 43  GR 11 CHEM M2 CHEMICAL AND METALLIC BONDING 5. Draw the outermost shell electron diagram of the following compound: i. O2 ii. HCl iii. Cl2 iv. N2 Thank you for completing your learning activity 7. Check your work. Answers are at the end of this module. REVISE WELL USING THE MAIN POINTS ON THE NEXT PAGE. 44  GR 11 CHEM M2 CHEMICAL AND METALLIC BONDING SUMMARY You will now revise this module before doing Assessment 6. Here are the main points to help you revise. Refer to the module topic if you need more information. Atom contains proton, neutrons and electrons. The nucleus is composed of protons; the positively charged particle and the neutrons, the particle with no charge. Around the nucleus is the electron, the negatively charged particle. Particle Charge Mass ( in atomic mass module) Proton 1+ 1 Neutron 0 1 electron 1- 0 ( almost)  Proton and neutrons have the same mass.  The electrons are so light that you can ignore their mass. The atomic structure Protons + Neutrons = Atomic Mass Number Symbol Number of Protons = Atomic Number Position of atomic mass and atomic number in the Periodic Table. 45  GR 11 CHEM M2 SUMMARY If we add up the RAM as in the formula, we get the Relative Formula Mass Electrons in orbit  The electrons orbit the nucleus in shells  The 1st shell can hold 2 electrons  The 2nd shell can hold 8 electrons. As can the 3rd shell The distribution of electrons among the orbitals of an atom is its electron configuration. S – sharp 2 electrons to fill p – principal 6 electrons to fill d – diffuse 10 electrons to fill f – fundamental 14 electrons to fill Total number of electrons in an energy level can be found by the formula: number of electrons = 2n2 Where n is the number of energy level; 1st = 2 2nd = 8 = (2+6) 3rd = 18 = (2 + +2+ 6 = 10) 4th = 32 = (2 + 6 + 10 + 14) 4f 5f 3d 4d 5d 6d 2p 3p 4p 5p 6p 7p 1s 2s 3s 4s 5s 6s 7s Electronic configuration 46  GR 11 CHEM M2 SUMMARY Below are some examples of electron configuration. Now I got! !it! Elements Atomic Number Electron Configuration Period Group 1.Hydrogen, H 1 1s1 1 IA 2.Lithium, Li 3 1s 22s1 2 IA 3.Berylium, Be 4 1s22s2 2 II A 4.Carbon, C 6 1s 22s22p2 2 IV A 5.Nitrogen, N 7 1s 22s22p3 2 VA 6.Aluminum, Al 13 1s22s22p63s23p1 3 III A 7.Sulfur, S 16 1s 22s22p63s23p4 3 VI A 8.Potassium, K 19 1s 22s22p63s23p64s1 4 IA 9.Bromine, Br 35 1s22s22p63s23p64s23d104p5 4 VII A Periodic Table The Development of Periodic table Johann Wolfgang Döbereiner showed that the atomic weight of strontium lies midway between those of calcium and barium. Some years later he showed that other such “triads” exist (chlorine, bromine, and iodine [halogens] and lithium, sodium, and potassium [alkali metals]). He also showed that similar relationships extended further than the triads of elements, fluorine being added to the halogens, and magnesium to alkaline-earth metals. Oxygen, sulfur, selenium, and tellurium were classed as one family, and nitrogen, phosphorus, arsenic, antimony, and bismuth as another family of elements. 1863, A.E.B, De Chancourtois proposed a classification of the elements based on the new values of atomic weights given by Stanislao Cannizzaro's system of 1858. De Chancourtois plotted the atomic weights on the surface of a cylinder with a circumference of 16 modules, corresponding to the approximate atomic weight of oxygen. The resulting helical curve brought closely. 400 BC Democritus suggest that all things are made of particles. 1805 John Dalton’s atomic theory. Atoms of the same element are alike. They combine to make compounds. 1909 Ernest Rutherford discover the proton. 1911 Ernest Rutherford discover the nucleus. 1913 Neil’s Bohr suggests those electrons are found in shells around the nucleus. 1932 James Chadwick proves that neutrons exist. 47  GR 11 CHEM M2 SUMMARY Periodic table The periodic table is a chart of all the known elements in order of increasing atomic number. The table puts elements into groups with similar characteristics, allowing us to recognize trends over the whole array of elements. Atom An atom is the smallest module of a substance that still has all the properties of that substance. Atomic number The atomic number of an atom is equal to the number of protons that the atom contains. Atomic weight/mass The atomic weight of an atom is a measure of how much mass an atom has. The atomic weight is calculated by adding the number of protons and neutrons together. Periodic Variations The groups ( Group 1 to 8) The periodic table is composed of 7 rows or periods and 18 major groups or columns. Elements in a group have similar properties particularly those elements in four of the groups: Group IA – The alkali metals; Group II A - the alkaline earth metals; Group VII A – the halogens and Group VIII A – the noble gases. Group IA The Alkali Metals Group 1 elements are soft and silvery metals. They react strongly with water. Group IIA The Alkaline Earth Metals This group consists of all metals that occur naturally in compound form. They are obtained from mineral ores and form alkaline solutions. These are less reactive than alkali metals. Group IIIA The Aluminum Group The elements in this group are fairly reactive. The group is composed of four metals and one metalloid which is boron. Group IVA The Carbon Group This group is composed of elements having varied properties because their metallic property increases from top to bottom meaning the top line. Group VA The Nitrogen Group Like the elements in group IV A, this group also consists of metals, nonmetal and metalloids. Group VIA The Oxygen Group This group is called the oxygen group since oxygen is the top line element. 48  GR 11 CHEM M2 SUMMARY Group VIIA The Halogens This group is composed of entirely nonmetals. The term halogen comes from the Greek word hals which means salt and genes which means forming. Halogens group are called salt formers. Group VIIIA The Noble Gases This group is composed of stable gases otherwise known as the non-reactive or inert elements. Bonding and Structures Chemical bonding The chemical bond formed by transfer of electron from a metal to a non- metal is known as ionic or electrovalent bond. Ionic bonds form between metals and non- metals. Properties of Ionic Compounds Physical State Ionic compounds are crystalline solids. In the crystal, the ions are arranged in a regular fashion. The ionic compounds are hard and brittle in nature. Melting and Boiling points Ionic compounds have high melting and boiling points. Electrical Conductivity Ionic compounds conduct electricity in their molten state and in aqueous solutions. Covalent bond forms by sharing electrons between non-metals. Covalent substances can have either a) Giant covalent structure or b) Simple molecular structure Properties of Covalent Substances The covalent compounds consist of molecules which are electrically neutral in nature.The forces of attraction present between the molecules are less strong as compared to the forces present in ionic compounds. Physical State Because of the weak forces of attraction present between discrete molecules, called intermolecular forces, the covalent compounds exist as a gas or a liquid or a solid. Melting and Boiling Points As the forces of attraction between the molecules are weak in nature, a small amount of energy is sufficient to overcome them. Hence, the melting points and boiling points of covalent compounds are lower than those of ionic compounds. 49  GR 11 CHEM M2 SUMMARY Electrical Conductivity The covalent compounds contain neutral molecules and do not have charged species such as ions or electrons which can carry charge. Therefore, these compounds do not conduct electricity and are called poor conductors of electricity. Metallic bonding are bonded together by sea of electrons. The electrons are free to drift between atoms. They move in one direction when electric current flow. Atoms are arranged in giant structures. Properties of the different types of chemical bonds Ionic Metallic Covalent Covalent Type of Giant Giant Giant Simple molecules structure Are ions Yes Yes No No present? Are delocalized No Yes No (except in No present? graphite) How strong is Strong Strong Very strong Very strong the chemical bond? High/Low High High Very high Low melting point Conductor of When molten/in Yes No (except graphite No electricity solution NOW YOU MUST COMPLETE ASSESSMENT 2 AND RETURN IT TO THE PROVINCIAL CENTRE CO-ORDINATOR. 50  GR 11 CHEM M2 SUMMARY ANSWERS TO LEARNING ACTIVITIES 1 - 7 Learning Activity 1 1. a) Proton b) Electron c) Neutron 2. Sub – atomic particles charge Mass ( atomic mass module) Proton 1+ 1 neutron 0 1 electron 1- 0 ( almost) 3. i. number of protons ns 7 number of electrons 7 number of neutrons 7 ii. number of protons 19 number of electrons 19 number of neutrons 20 Iii. number of protons 10 number of electrons 10 number of neutrons 10 51  GR 11 CHEM M2 ANSWERS TO LEARNING ACTIVITIES Learning Activity 2 1. i. Atom of the same element with the same number of protons but different number of neutrons. ii. Used to separate the different atoms or isotopes of an element. 2. i. 63 x 69 + 65 x 31 100 = 63.62 ii. 16 x 99.79 + 17 x 0.04 + 18 x 0.20 100 = 16.0092 Learning Activity 3 1. Show how the electrons are arranged in the selected element and the distribution of electrons among the orbital’s of an atom. 2. Draw the electron configuration of the following using the s, p, d and f. i. Na = 1s22s22p63s1 ii. Ca = 1s22s22p63s23p64s2 iii. Cl = 1s22s22p63s23p5 iv. Zn = 1s22s22p63s23p64s23d10 v. F = 1s22s22p5 vi. Al = 1s22s22p63s23p1 Learning Activity 4 1. i. Is the smallest module of a substance. ii. Is the total number of protons and neutrons. iii. The total number of protons in the nucleus of an atom. 2. 1932 3. Neil’s Bohr 52  GR 11 CHEM M2 ANSWERS TO LEARNING ACTIVITIES Learning Activity 5 1. i. Possess the properties of both the metals and non-metals. ii. The energy required to remove the outer electron from an isolated atom. iii. Is the energy released when neutral atoms gain an extra electron to form negatively charged ion. iv. The electron attracting ability to an atom. 2. i. Atoms get larger going down a group. ii. Atoms get smaller moving from left to right across each period. 3. Elements are arranged from the lightest to heaviest. Learning Activity 6 1. Alkali group 2. Because their atoms have already have a stable outer most electron shell. 3. Draw the atomic structure of the following and elements and identify what group and period they belong? a) Zn 2 18 8 2 Zn n Group 2 Period 4 53  GR 11 CHEM M2 ANSWERS TO LEARNING ACTIVITIES b) Al 3 8 2 Al Group 3 Period 3 c) F 2 7 F Group 7 Period 2 Learning Activity 7 1. Name the ions present in sodium chloride. i. Chloride ii. Sodium 2. 2 3. 18 4. By sharing of electrons. 54  GR 11 CHEM M2 ANSWERS TO LEARNING ACTIVITIES 5. i.O2, XX XX X X + X X X XX X O O O O X X X X X X XX XX XX XX XX O2 ii. HCl, XX XX =++ X X X Cl X + X Cl X H H XX XX H + Cl HCl ii. Cl2 XX XX XX XX X Cl X ++++ Cl X X Cl X Cl X X X X X X X XX XX XX XX + Iv.N2. XX X + X X X X X N XX N X N X X N XX X XX XX 55  GR 11 CHEM M2 ANSWERS TO LEARNING ACTIVITIES REFERENCES ELVINS, C., JONES, D., LUKINS, N., MISKIN, J., ROSS, B., & SANDERS, R. (1990). CHEMISTRY ONE: MATERIALS, CHEMISTRY IN EVERYDAY LIFE. PORT MELBOURNE, AUSTRALIA: HEINEMANN EDUCATIONAL AUSTRALIA BUCAT, R.B. (ED.) (1984). ELEMENTS OF CHEMISTRY: EARTH, AIR, FIRE & WATER, VOLUME 2. CANBERRA CITY, A.C.T., AUSTRALIA: AUSTRALIAN ACADEMY OF SCIENCE HEYWORTH, R. M. (2000). EXPLORE YOUR WORLD WITH SCIENCE DISCOVERY 1. FIRST LOK YANG ROAD, SINGAPORE. PEARSON EDUCATION SOUTH ASIA PTE LTD BRADY, J.E. & SENESE, F. (2004). CHEMISTRY: MATTER AND ITS CHANGES, 4TH EDITION. RIVER STREET HOBOKEN, NJ: JOHN WILEY & SONS, INC GALLAGHER, R. & INGRAM, P. (1989). CO-ORDINATED SCIENCE: CHEMISTRY. OXFORD, ENGLAND: OXFORD UNIVERSITY PRESS HILL, J.W. & KOLB, D.K. (1998). CHEMISTRY FOR CHANGING TIMES, 8TH EDITION. UPPER SADDLE RIVER, NJ: PRENTICE HALL Araneta, F.L., Catris, L.V. & Deauna, M.C. (2002). The world of chemistry III. (2nd ed.) Quezon City: SIBS Publishing House, Inc. Chang, R. (2005). Chemistry. (8th ed.) New York: Mc Graw-Hill Companies Rosemarie Gallager and Paul Ingram Complete Chemistry for Cambridge IGCSE Laurie Ryan Chemistry for you national Curriculum Edition for GCSE World of chemistry John W. Wilkinson gjascience.wordpress.com1071 www.slideshare.net slideplayer.com960 56  FODE PROVINCIAL CENTRES CONTACTS FODE CUG PHONE CUG PHONE PC NO. PROVINCIAL ADDRESS PHONE/FAX (COORDINATOR) (SENIOR CLERK) CENTRE P. O. Box 822, 1 ALOTAU 6411343/6419195 72228130 72229051 Alotau P. O. Box 154, 2 BUKA 9739838 72228108 72229073 Buka 72229050 3 CENTRAL C/- FODE HQ 3419228 72228110 4 DARU P. O. Box 68, Daru 6459033 72228146 72229047 P. O. Box 990, 5 GOROKA 5322085/5322321 72228116 72229054 Goroka 6 HELA P. O. 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