Ch 2 ATOMS, MOLECULES, AND IONS

2.1 Atomic Theory of Matter Democritus- atomos- tiny indivisible particles Dalton- Atomic Theory Element composed of atoms Atoms in element are identical Chemical reactions involve reorganizations of atoms. Atoms are not changed in a chemical reaction. Compounds are formed when atoms of more than 1 element combine, a given cmpd always has the same relative numbers and kinds of atoms

Chemical Laws Dalton used to build postulates Law of Constant Composition- a given compound always contains the same proportions of elements by mass Law of Conservation of Matter- matter is netiher created nor destroyed. Law of Multiple Proportions- when two elements form more than one compound, the different masses of one element that are combined with the same mass of the other element are in a ratio of small whole numbers. Ex-CO g of oxygen to 1 g of carbon CO g of oxygen to 1 g of carbon 2.66 g : 1.33 g = 2:1 ratio

Discovery of Atomic Structure JJ Thompson and the Electron Experiments w/ CRT Determined charge to mass ratio of e- “Plum Pudding Model” Robert Millikan and the Oil-Drop Determined the charge of an e- Using Thompson’s charge/ mass ratio, he determined mass of e- (9.1 x g)

Radioactivity- Becquerel, Curie, Rutherford  Rays- high energy light  Particles- high speed e-  Particles- He nucleus Nuclear Atom and Rutherford’s Foil Experiment Positively charged center Disproved Thompson’s model

2.3 Modern Atomic Structure Nucleus- small size, high density (pea w/ a mass of 250 million tons) Protons- positive Neutrons- neutral Electrons Negative Reactivity of elements Responsible for most of atom’s volume

Atomic number # of protons Element’s identity Mass number Protons + neutrons Isotopes Same proton #, different neutron #  Ex- carbon-12, carbon-14

2.4 Atomic Weights Average atomic mass Accounts for abundancies of all isotopes Ex- Carbon  98.93% 12 C and 1.07% 13 C (0.9893)(12 amu) + (0.0107)( amu) = amu

2.5 The Periodic Table Organization Horizontal row- period  Same outer energy level Vertical column- group or family  Same # of valence electrons, similar properties  Group 1A- alkali metals  Group 2A- alkaline earth metals  Group 7A- halogens  Group 8A- noble gases Metals, nonmetals, metalloids

2.6 Molecules and Molecular Compounds Covalent bonds Between 2+ nonmetals 7 Diatomic molecules- 2 atoms of same element “Mr. BrINClHOF” Molecular formulas vs empirical formulas Molecular- actual # and types of atoms  Ex- hydrogen peroxide- H 2 O 2, glucose- C 6 H 12 O 6 Empirical- relative # and types of atoms, reduced to lowest whole # ratios  Ex- hydrogen peroxide- HO, glucose- CH 2 O

3 ways to view molecules Ball and Stick Model Structural Formula Space Filling Model

2.7 Ions and Ionic Compounds Cation- positive Loss of e- Metals (Group 1A, 2A, Al, H) Anion- negative Gain of e- Nonmetals (Group 6A, 7A, N, H) Polyatomic ions Group of covalently bonded atoms with a net + or - charge

Attraction between cations and anions form ionic compounds Typically btwn metal and nonmetal Electrically neutral Conduct electricity Usually solid Empirical formulas Use “criss-cross” method- charge of one ion (ignore the sign) becomes the subscript of the other one (reduce if needed!)

2.8 Naming Inorganic Compounds Ionic Positive ion first, negative second (-ide suffix) Memorize polyatomics!  Find “-ate” ion chlorate = ClO 3 -  “ite” is 1 less O than “ate” chlorite = ClO 2 -  Prefix “per” is 1 more O than “ate” perchlorate = ClO 4 -  Prefix “hypo” is 1 less O than “ite” hypochlorite = ClO - Metals with more than one oxidation state (transition metals) must have a romal numeral to indiate the oxidation state  Ex- Fe +3 = iron (III)

Binary covalent Must contain 2 elements, BOTH nonmetals First element  Full name  Prefix ONLY if more than 1 Second element  Named as if it were an anion (-ide suffix)  ALWAYS gets a prefix

Acids Binary acids (HX)  “hydro” + root of second element + “ic”  Ex- H 2 Shydrosulfuric acid Oxyacids  Acid contains anion that ends in “ate”  Root of anion name + “ic”  HNO 3 nitric acid  Acid contains anion that ends in “ite”  Root of anion name + “ous”  HNO 2 nitrous acid

2.9 Simple Organics Hydrocarbons- only contain C and H Alkanes Class of hydrocarbons where each C bonded to 4 other atoms  Methane (CH 4 ), ethane (C 2 H 6 ), propane (C 3 H 8 )  Compounds with 5+ carbons use prefix plus –ane ending  Ex- C 8 H 18 octane Alcohols H is replaced with an –OH group Use alkane root with –ol suffix  Methanol, ethanol, propanol When 3+ C, need to specify which carbon has –OH with a #  1 represents outer C, 2 inner, etc….  1-propanol, 2-propanol