A.P. Ch. 2 Review Work

Atoms, Molecules, Ions

• Conservation of mass: during a reaction the amount of material you start with equals the amount you end with

Dalton’s Atomic Theory• 1. Elements made of atoms • 2. Atoms of same elements identical, different

elemental atoms are different • 3. Compounds are atoms combined • 4. Chemical rxns: reorganization of atoms • 5. Cannot change one element into another

through chemical rxn

Thomson’s Experiment• Electrified gas in a cathode ray tube sends a beam

from anode (- end) to cathode (+ end)

• When a positive charge is presented to the light beam, it is bent towards charge

• Thomson reasoned beam made of negatively charge particles he called “electrons”

• Identified their charge to mass ratioPositive Magnet

Rutherford’s Experiment• Used radioactive particles shot at a piece of

gold foil to determine the composition of atoms

• Based on “Plum-Pudding Model” of atom, assumed particles go through with few deflections

• Most particles went through, yet some large deflections, indicating atoms made of mostly space with dense part

Atomic Particles• Protons: positively charged in nucleus• Neutrons: no charge in nucleus• Electrons: negatively charged around nucleus

Molecules• Multiple atoms joined together by covalent bonds

• Covalent bond: e- shared by attached atoms

• Ionic bond: electrostatic attraction between oppositely charged ions (when e- lost or gained by an atom), different elements joined form “compounds”

• Lose e- (+ ion “Cation”)

• Gain e- (- ion “Anion”)

Covalent bond

Ionic bond

Periodic Table• Organized by # of protons

• Vertical columns (“groups”) based on similar properties

• Horizontal rows (“periods”) based on similar electron organizations

Determining Ionic Charges• Based on periodic table location

• Atoms are more stable with optimum number of electrons in their outer orbits (usually 8)

• They can take in electrons to reach this # or lose some to make their next inner orbit full

Outer e- 1 2 3 4 5 6 7 8

Charge +1 +2 +3 +/-4 -3 -2 -1 0

Nomenclature (“Naming”)• Binary (type I) Ionic compounds:

Cation keeps name, Anion has –ide endingSodium + Chlorine = (NaCl)

( )

Na + Cl2 NaCl

• Binary (type II) Ionic compounds:

If cation has more than one positive state (some transition metals, see table 2.4) then must use roman numeral to show actual charge

Iron + oxygen = (FeO)

Iron + oxygen = (Fe2O3) Fe + O2 FeO

Fe + O2 Fe2O3

If anion has more than one atom in it (polyatomic ion), it has a special ending other than –ide (see table 2.5)

Mg(OH)2 =

• Binary (Type III) Covalent Compounds:Same rules as type I but need prefixes to indicate how many atoms of each

C2H2 =

CO2 = (“Mono” never precedes first atom)

Mono, Di, Tri, Tetra, Penta, Hexa, Hepta, Octa, Nona, Deca

• Acid Names:

Acids usually preceded by Hydrogen

Acid names depend on anion ending

1. Ending “-ide” Hydro _anion prefix_ ic Acid

Ex. HCl =

2. Ending “-ate” Anion prefix ic Acid

Ex. H2SO4 =

3. Ending “-ite” Anion prefix ous Acid

Ex. H2SO3 =