Chapt02_lecture.pdf

General Chemistry for Health Sciences Dr. Montaha Anjass Almasri Assistant Professor Department of Chemistry University of Sharjah [email protected] www.anjassgroup.net 1  Content 1. Chapter 1. Chemistry: Methods and Measurements 2. Chapter 2. The Structure of Atoms and the Per...

General Chemistry for Health Sciences Dr. Montaha Anjass Almasri Assistant Professor Department of Chemistry University of Sharjah [email protected] www.anjassgroup.net 1  Content 1. Chapter 1. Chemistry: Methods and Measurements 2. Chapter 2. The Structure of Atoms and the Periodic Table 3. Chapter 3. Structure and Properties of Ionic and Covalent Compounds 4. Chapter 4. Calculations and the Chemical Equation 5. Chapter 5. States of Matter: Gases, Liquids, and Solids 6. Chapter 6. Solutions 7. Chapter 7. Energy, Rate, and Equilibrium 8. Chapter 8. Acids and Bases and Oxidation Reduction 9. Chapter 9. The Nucleus, Radioactivity, and Nuclear Medicine General, Organic and Biochemistry, K. Denniston and D. Quirk 8th Edition 2  GENERAL CHEMISTRY General, Organic and Biochemistry 8th Edition Copyright© The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 2.1 Composition of the Atom Atom - the basic structural unit of an element The smallest unit of an element that retains the chemical properties of that element 2.1 Composition of the Atom Electrons, Protons and Neutrons Atoms consist of three primary particles electrons 1 protons neutrons Nucleus - small, dense, positively charged region in the center of the atom containing: - protons - positively charged particles - neutrons - uncharged particles 2.1 Composition of the Atom Characteristics of Atomic Particles Electrons are negatively charged particles located outside of the nucleus of an atom Protons and electrons have charges that are equal in magnitude but opposite in sign A neutral atom that has no electrical charge has the same number of protons and electrons Electrons move very rapidly in a relatively large volume of space while the nucleus is small and dense 2.1 Composition of the Atom Symbolic Representation of an Element 2 Mass Number A Atomic Z X Symbol of Number the atom Atomic number (Z) - the number of protons in the atom Mass number (A) - sum of the number of protons and neutrons 2.1 Composition of the Atom Atomic Calculations mass number = number of protons + number of neutrons number of neutrons = mass number - number of protons number of neutrons = A − Z 2.1 Composition of the Atom Selected Properties of the Three Basic Subatomic Particles Name Charge Mass(amu) Mass (grams) Electrons (e) −1 5.4  10-4 9.1095  10-28 Protons (p) +1 1.0 1.6725  10-24 Neutrons (n) 0 1.0 1.6750  10-24 2.1 Composition of the Atom Determining the Composition of an Atom Calculate the number of protons, neutrons and electrons in each of the following: 2 11 5 B 55 26 Fe 2.1 Composition of the Atom Isotopes Isotopes - atoms of the same element having different masses – contain same number of protons 4 – contain different numbers of neutrons 3 Isotopes of Hydrogen Hydrogen Deuterium Tritium (Hydrogen - 1) (Hydrogen - 2) (Hydrogen - 3) 2.1 Composition of the Atom Isotopic Calculations Isotopes of the same element have identical chemical properties Some isotopes are radioactive Find chlorine on the periodic table What is the atomic number of chlorine? 17 What is the mass given 35.45 This is not the mass number of an isotope 2.1 Composition of the Atom Atomic Mass What is this number, 35.34? The atomic mass - the weighted average of the masses of all the isotopes that make up chlorine Chlorine consists of chlorine-35 and chlorine-37 in a 3:1 ratio Weighted average is an average corrected by the relative amounts of each isotope present in nature 2.1 Composition of the Atom Determining Atomic Mass 3 Calculate the atomic mass of naturally occurring chlorine if 75.77% of chlorine atoms are 35Cl and 24.23% of chlorine atoms are 37Cl Step 1: convert the percentage to a decimal fraction 75.77% 35Cl = 0.7577 35Cl 24.23% 37Cl = 0.2423 37Cl 2.1 Composition of the Atom Step 2: Multiply the decimal fraction by the mass of that isotope to obtain the isotope contribution to the atomic mass. For 35Cl: 0.7577 x 35.00 amu = 26.5 amu For 37Cl: 0.2423 x 37.00 amu = 8.97 amu Step 3: sum these partial weights to get the weighted average atomic mass of chlorine: 26.52 amu + 8.965 amu = 35.5 amu 2.1 Composition of the Atom Atomic Mass Determination Neon has three naturally occurring isotopes Mass Abundance 20Ne 20.0 amu 90.48% 21Ne 21.0 amu 0.27% 22Ne 22.0 amu 9.25% What is the atomic mass of Neon?  2.4 The Periodic Law and the Periodic Table 7 Dmitri Mendeleev and Lothar Meyer - two scientists working independently developed the precursor to our modern Periodic Table. They noticed that as you list elements in order of atomic mass, there is a distinct regular variation of their properties. Periodic Law - the physical and chemical properties of the elements are periodic functions of their atomic numbers. 2.4 The Periodic Law and the Periodic Table Classification of the Elements  Parts of the Periodic Table and the Periodic Table 2.4 The Periodic Law Period – a horizontal row of elements in the periodic table. They contain 2, 8, 8, 18, 18, and 32 elements, 7 Group – also called families are columns of elements in the periodic table. Elements in a particular group or family share many similarities, as in a human family.  Category Classification of and the Periodic Table 2.4 The Periodic Law Elements 7 Metals - elements that tend to lose electrons during chemical change, forming positive ions. Nonmetals - a substance whose atoms tend to gain electrons during chemical change, forming negative ions. Metalloids - have properties intermediate between metals and nonmetals.  Classification of Elements and the Periodic Table Metals 2.4 The Periodic Law Metals: 7 – A substance whose atoms tend to lose electrons during chemical change – Elements found primarily in the left 2/3 of the periodic table Properties: – High thermal and electrical conductivities – High malleability and ductility – Metallic luster – Solid at room temperature  Classification of Elements and the Periodic Table 2.4 The Periodic Law Nonmetals 7 Nonmetals: – A substance whose atoms may gain electrons, forming negative ions – Elements found in the right 1/3 of the periodic table Properties: – Brittle – Powdery solids or gases – Opposite of metal properties  Atomic Number and Atomic Mass and the Periodic Table 2.4 The Periodic Law 8 Atomic Number: – The number of protons in the nucleus of an atom of an element – Nuclear charge or positive charge from the nucleus Most periodic tables give the element symbol, atomic number and atomic mass  Element Information in the and the Periodic Table 2.4 The Periodic Law Periodic Table 20 atomic number Ca symbol Calcium name 40.08 atomic mass  Using the Periodic Table and the Periodic Table 2.4 The Periodic Law Identify the group and period to which each of the following belongs: a. P b. Cr c. Element 30 How many elements are found in period 6? How many elements are in group VA?  2.5 Electron Arrangement and the Periodic Table 9 The electron arrangement is the primary factor in understanding how atoms join together to form compounds Electron configuration - describes the arrangement of electrons in atoms Valence electrons - outermost electrons – The electrons involved in chemical bonding 2.5 Electron Arrangement The Quantum Mechanical Atom and the Periodic Table Bohr’s model of the hydrogen atom didn’t clearly explain the electron structure of other atoms – Electrons in very specific locations, principal energy levels – Wave properties of electrons conflict with specific location Schröedinger developed equations that took into account the particle nature and the wave nature of the electrons 2.5 Electron Arrangement Schröedinger’s equations and the Periodic Table Equations that determine the probability of finding an electron in specific region in space, quantum mechanics – Principle energy levels (n = 1,2,3…) – Each energy level has one or more sublevels or subshells (s, p, d, f) – Each sublevel contains one or more atomic orbitals 2.5 Electron Arrangement Energy Levels and Sublevels and the Periodic Table PRINCIPAL ENERGY LEVELS n = 1, 2, 3, … The larger the value of n, the higher the energy level and the farther away from the nucleus the electrons are The number of sublevels in a principal energy level is equal to n – in n=1, there is one sublevel – in n = 2, there are two sublevels 2.5 Electron Arrangement Principal Energy Levels and the Periodic Table The electron capacity of a principal energy level (or total electrons it can hold) is 2(n)2 – n = 1 can hold 2(1)2 = 2 electrons – n = 2 can hold 2(2)2 = 8 electrons How many electrons can be in the n = 3 level? – 2(3)2 = 18 Compare the formula with periodic table….. 2.5 Electron Arrangement Sublevels and the Periodic Table Sublevel: a set of energy-equal orbitals within a principal energy level Subshells increase in energy: s