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Atoms, Molecules, and Ions

Atoms, Molecules, and Ions

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Atoms, Molecules, and Ions

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  1. Atoms, Molecules, and Ions Ch 2

  2. 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

  3. 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- 1.33 g of oxygen to 1 g of carbon CO2- 2.66 g of oxygen to 1 g of carbon 2.66 g : 1.33 g = 2:1 ratio

  4. 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 10-28 g)

  5. Radioactivity- Becquerel, Curie, Rutherford • g Rays- high energy light • b Particles- high speed e- • a Particles- He nucleus • Nuclear Atom and Rutherford’s Foil Experiment • Positively charged center • Disproved Thompson’s model

  6. 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

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

  8. 2.4 Atomic Weights • Average atomic mass • Accounts for abundancies of all isotopes • Ex- Carbon • 98.93% 12C and 1.07% 13C (0.9893)(12 amu) + (0.0107)(13.00335 amu) = 12.01 amu

  9. 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

  10. 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- H2O2, glucose- C6H12O6 • Empirical- relative # and types of atoms, reduced to lowest whole # ratios • Ex- hydrogen peroxide- HO, glucose- CH2O

  11. 3 ways to view molecules Space Filling Model Ball and Stick Model Structural Formula

  12. 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

  13. 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!)

  14. 2.8 Naming Inorganic Compounds • Ionic • Positive ion first, negative second (-ide suffix) • Memorize polyatomics! • Find “-ate” ion chlorate = ClO3- • “ite” is 1 less O than “ate” chlorite = ClO2- • Prefix “per” is 1 more O than “ate” perchlorate = ClO4- • 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)

  15. 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

  16. Acids • Binary acids (HX) • “hydro” + root of second element + “ic” • Ex- H2S hydrosulfuric acid • Oxyacids • Acid contains anion that ends in “ate” • Root of anion name + “ic” • HNO3 nitric acid • Acid contains anion that ends in “ite” • Root of anion name + “ous” • HNO2 nitrous acid

  17. 2.9 Simple Organics Hydrocarbons- only contain C and H Alkanes Class of hydrocarbons where each C bonded to 4 other atoms Methane (CH4), ethane (C2H6), propane (C3H8) Compounds with 5+ carbons use prefix plus –ane ending Ex- C8H18 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