Unit 1 Chemistry Notes 2020 PDF

Elements, Compounds, Groups on the Periodic Table A Table of the Elements: An element is a pure substance that cannot be broken down. It is composed of only one type of atom. An element symbol is an abbreviation for a chemical element that can be represented by one or two letters. H = Hydrogen,...

Elements, Compounds, Groups on the Periodic Table A Table of the Elements: An element is a pure substance that cannot be broken down. It is composed of only one type of atom. An element symbol is an abbreviation for a chemical element that can be represented by one or two letters. H = Hydrogen, He = Helium Some elements on the periodic table have abbreviations that are based on their Latin names. Symbol Name Latin Na Sodium Natrium K Potassium Kalium A Table of the Elements You will need to know the following elements for the quiz: 1-20,26,28,29,30,35,47,50,74,79,80,82 A compound is a pure substance that contains two or more different elements that are chemically joined. Ex. Water (H2O) A molecule can be an element or a compound. It consists of two or more atoms (same or different) combined together. An alloy is a solid of two or more metals. 1 WHAT IS A PERIODIC TABLE? The periodic table is an arrangement of the chemical elements, organized on the basis of their atomic number (number of protons in the nucleus), electron configurations, and recurring chemical properties. Elements are presented in order of increasing atomic number, which is typically listed with the chemical symbol in each box. The standard form of the table consists of a grid of elements laid out in 18 columns and 7 rows, with a double row of elements below that. The rows of the table are called periods; the columns are called groups, with some of these having names such as halogens or noble gasses. The table can be used to derive relationships between the properties of the elements and predict the properties of new, yet to be discovered or synthesized (man- made), elements. Although precursors exist, Dmitri Mendeleev is generally credited with the publication, in 1869, of the first widely recognized periodic table. He developed his table to illustrate periodic trends in the properties of the then-known elements. Mendeleev also predicted some properties of then-unknown elements that would be expected to fill gaps in this table. 2 1. Atoms in a molecule can be all the same kind of atom Example - O2 2. Molecules can also be made of two or more different kinds of atoms. Example - CO2, H2O Patterns in the Periodic Table: When you go to the supermarket, how do you find the foods on your shopping list? If you are looking for yogurt or milk, you look for the aisle marked “Dairy Products”. For potatoes or carrots, you look for the “Fruits and Vegetables” aisle. Food in the supermarket is arranged so that people can find things quickly and easily. 3 4 5 6 7 8 9  Atomic Theory Ancient theory: Anaxagoras (Greek, born 500 B.C.) – Suggested every substance had its own kind of “seeds” that clustered together to make the substance, much as our atoms cluster to make molecules. Empedocles (Greek, born in Sicily, 490 B.C.) – Suggested there were only four basic seeds – earth, air, fire, and water. The elementary substances (atoms to us) combined in various ways to make everything. Democritus (Thracian, born 470 B.C.) – Actually proposed the word atom (indivisible) because he believed that all matter consisted of such tiny units with voids between, an idea quite similar to our own beliefs. It was rejected by Aristotle and thus lost for 2000 years. Aristotle (Greek, born 384 B.C.) – Added the idea of “qualities” – heat, cold, dryness, moisture – as basic elements which combined as shown in the diagram (previous page). – Hot + dry made fire; hot + wet made air, and so on. Alchemy: After that chemistry was ruled by alchemy. They believed that that could take any cheap metals and turn them into gold. Alchemists were almost like magicians. – elixirs, physical immortality – led to scientific inquiry skills and formation of new equipment. – Develop lab apparatus / procedures / experimental techniques: 10  - alchemists learned how to prepare acids. - developed several alloys - new glassware o Grouping Elements In 1789 Antoine Lavoisier grouped 33 elements as: gasses, metals, non‐metals and earths. In 1808 John Dalton published his theory –called atomic model for matter In 1829 Johann Dobereiner‐ more specific classification: ▪ -grouped based on their chemical properties ▪ -grouped lithium, sodium, and potassium as soft reactive metals. In 1831 Michael Faraday found that electric current could cause chemical changes in some compounds in solution….led to the discovery of ions. In 1869 Dimitri Mendeleev gathered information on all known elements and grouped them based on increasing atomic mass…..which later changed increasing to atomic number. In 1897 JJ Thomson revised the atomic model (Raison bun model / plum pudding model) In 1911 Ernest Rutherford undertook the gold foil experiment to improve the nuclear model He worked with Niels Bohr to produce Bohr diagrams that resemble the planetary model of our solar system. 11 Mendeleev and the First Periodic Table Mendeleev 1869 Created cards for 64/69 known elements Arranged elements in order of atomic mass 1 long line but noticed repeating properties Grouped similar properties into rows Left gaps where properties did not match and predicted elements would be there one day Flipped some elements (mass lower) because of properties 12 Mendeleev’s Periodic Law: If the elements are arranged according to their atomic mass, a pattern can be seen in which similar properties occur regularly. -was a major breakthrough in the understanding of the elements but……it didn’t always work… so he concluded his calculations were flawed and went with his instincts to arrange elements based on their properties. 13 Modern Periodic Law: If the elements are arranged according to their atomic number, a pattern can be seen in which similar properties occur regularly. 14  MENDELEEV’S PERIODIC TABLE Mendeleev’s original periodic table included 63 chemical elements. On his table, Mendeleev showed that, when arranged by atomic weight, the elements display a periodicity of properties. The table organized the elements in groups vertically. Mendeleev’s table had blank spaces as placeholders to represent unknown elements. By following the trends of the table, he was able to determine characteristics of new elements. When the elements were discovered later, Mendeleev’s predictions came true. 15 16 Understanding the Atomic Model: Actually, there are several "models" of the atom, not just one. The reason we talk about a "model," rather than about an atom directly, is because we can't really SEE an atom, so we can only guess about how it actually works inside. When our model makes sense and seems to explain what we see when we do an experiment, we say that our model is good. If our model doesn't explain what we see, then we have to change our model until it does explain what we see. Here are several models of the atom as they were developed in history:.................................. 17 18  Subatomic Particles Sub / atomic= Under-below/atom Means anything that is found within an atom There are 3 subatomic particles (grade 9):(36 as of this moment in the real world 2023) Proton Electron Neutron The Atom nucleus is the central core Protons are subatomic particles with a positive charge a relative mass of 1 located in the nucleus Neutrons are neutral subatomic particles a relative mass of 1 located in the nucleus Electrons are subatomic particles with a negative charge, 1/2000 (1/1836) of the mass of a proton or a neutron located in the orbits of the atom. 19 Standard notation We will learn how to read numbers today Remember the fun times we had on a teeter totter 1p 1836e ___________________ Protons are + + If I want a neutral overall charge…. I need 2 negatives …. Therefore I would have 2 electrons - - ++ -- The only remaining subatomic particle is the neutron The # of neutrons = Mass # - Atomic # n0= m# -a#.... but man how do we find the mass # and atomic 20 Example) Magnesium- Mg , metal, alkali earth metal, 12, 24.305 round 24 Mass # M 24 Atomic # A 12.. this is called standard notation..this is called a Bohr-Rutherford model 21 ex Lithium Mass # M Atomic # A 22 Bohr diagrams How to draw Bohr Diagrams: Bohr diagrams show electrons orbiting the nucleus of an atom somewhat like planets orbit around the sun. In the Bohr model, electrons are pictured as traveling in circles at different levels, depending on which element you have. (In real life, electrons do NOT travel in circles as pictured in Bohr Diagrams, but the diagrams are very useful for discussing certain aspects of chemical behavior, so we use them frequently for that purpose.) Here are some examples of Bohr diagrams: (These show the atoms lithium, fluorine and aluminum.) 23 24 25 Isotopes and Radioisotopes Atoms with the same element have different numbers of neutrons are called isotopes. Some isotopes are radioactive and are therefore described as radioisotopes or radionuclides Due to isotopes, mass #s are not round #s. Li (6.9) is made up of both 6Li and 7Li. Often, at least one isotope is unstable. Bohr Diagrams and Reactivity Column 8...the noble gases...are not reactive WHY? What is similar about electrons in outer shell as you move down a group? What happens to the radius of the atom as you move down a group? What happens to # of electrons in outer shell as you move across a period? Therefore reactivity increases as you move down a group because.....there are more shells which house more electrons Therefore reactivity decreases as you move across a period because...there are more electrons in the outer shell 26 Gas Tests Grade 9 Science Chemistry – 3 Gas Tests Test # 1 – Glowing wood splint is placed into a test tube with pure oxygen gas. Prediction Explanation Observation- Explanation Test # 2 – Burning splint is placed into a test tube with pure hydrogen gas. Prediction Explanation Observation Explanation when metals(magnesium) are placed into an acid……hydrogen gas is produced…..hydrogen gas is flammable(burns) so when I insert a burning splint….it ignites(burns) and we hear a popping sound like it was just performed 27 Test # 3 – Carbon dioxide gas is bubbled into limewater (Ca(OH)2) Prediction: Explanation: Observation: took a straw and placed into a beaker. The beaker contained a clear liquid(limewater). The solution became cloudy(foggy) Explanation a chemical reaction occurs because our breath contains Carbon Dioxide 28 Counting Atoms: What are the elements and number of atoms? a) H2O b) C3H8 c) C6H12O6 d) 3CH4 e) 2Mg1(OH)2 a) H2O1 2- Hydrogen and 1-oxygen, for a total of 3 total atoms b) C3H8 3 Carbon and 8 hydrogen, for a total of 11 total atoms c) C6H12O6 6 carbon 12 hydrogen 6 oxygen, for a total of 24 atoms d) 3CH4 = CH4 CH4 CH4 = CHHHH CHHHH CHHHH (gather like terms) 3 Carbon 12 hydrogen, for a total of 15 atoms 3(C1H4) distributive property which states…….x everything out by everything in 3 carbon 12 hydrogen 29 e) 2Mg1(OH)2 = Mg1(OH)2 Mg1(OH)2 Mg OH OH Mg OH OH 2 magnesium 4 oxygen 4 hydrogen =2Mg 4H 4O 2(Mg1(O1H1)2 ) 2(1 Mg 2O 2H) 2Mg 4O 4H Molecules: two or more atoms are joined together. diatomic molecules (molecular elements) (O2, N2) (also H2, F2, Cl2, Br2, I2 form this type of molecule) HOFBrINCl= diatomic molecules Chemical formula type and numbers of atoms in a molecule Molecular compounds have two or more types of elements bonded together hydrocarbon- is an organic compound consisting entirely of hydrogen and carbon Ex) methane CH4, ethane C2H6 *****Molecular models activity lab 30 Bonding What is a bond? -attachment -hang out -together -to put together…. -money -relationship -connection -feelings -ties In science, when we talk about the word bond we mean the combination of elements to produce a new compound. There are two kinds of Bonds (for this class) A) Ionic Bonds- Metal + Non-metal Lose/gain electrons- 1 sided relationship 31 High melting point Good conductor B) Molecular/Covalent Bonds- 2 Non-metals that share electrons. Low melting points Good conductors Types of Ions……….IONS ARE CHARGED ATOMS GENLEP gain electrons negative/lose electrons positive. There are 2 kinds of ions- any charged atom…. A) positive if we lose electrons- CATION(cats have paws) Mg+2, Na+1, Ca+2 B) negative if we gain electrons-ANION O -2, N -3, S -2 FORMING COMPOUNDS 1 2 34 3 2 1 0 bonds that an atom can make 1 2 34 5 6 7 8 valence electrons(valence Shell) Li Be B C NO F 32 1. IONIC Cross over method The compounds we will form are ionic compounds. Here are the steps: Cross over method 1) write the symbol 2) write the number of bonds 3) cross the # behind and below 4) name: metal first then non-metal ending in “ide” Consider the following examples: ex) Magnesium reacts with Chlorine 2 1 Mg Cl Mg1Cl2 Magnesium Chlorine becomes Magnesium Chloride 33 ex) Magnesium reacts with Oxygen 2 2 Mg O Mg2O2 reduce Mg1O1 OR MgO Magnesium Oxygen becomes Magnesium Oxide ex) Magnesium and Nitrogen react 2 3 Mg N Mg3N2 Magnesium Nitrogen becomes Magnesium Nitride 34 2. MOLECULAR The next compounds we will form are molecular (covalent) compounds. Remember if I say molecular….it is 2 non-metals Ex) Oxygen and Chlorine react 2 1 O Cl O1Cl2 Ex) Nitrogen and Oxygen react 3 2 N O N2O3 diNITROGEN triOXIDE 35 *****Next year we will introduce terms called prefixes in grade 10 Ex) Now you try: Li reacts with O Ca reacts with P Al reacts with N Review questions: Page 202#1,3,7,10,16,17,18,19 Page 204#1-11,15,16,25 Page 248#2,5,7,10,11b, Page 250#1,3,4,10,11,15,20 Page 282#1-13,19 Page 288#1-42,43,44,45,46,52,55,74,77,78 Page 294#1-10,15,16,21,23 36 37