Ch 2 Atoms/Molecules

Basic structure

John Daltons-Atomic theory JJ Thomson/Crookes-Cathode Ray

Tube Experiments & Plum pudding model

Rutherford-Gold Foil Experiment Millikin’s Oil Drop Experiment

Protons mass = 1 amu charge +1

Neutrons mass = 1 amucharge 0

Electrons mass = negligible charge -1

Amu = atomic mass unit. 1 amu = _____________ grams

Txt pg

Protons mass = 1. 0073 amu charge = +1.69 x 10- 19

Coulumbs (+1 Charge)

Nuetronsmass = 1.0087 amu charge = 0

Coulumbs

Electronsmass = 0.0005486 amu charge = -1.69 x 10- 19 Coulumbs

(-1 Charge)1.0073 amu1.0087 amu0.00005486 amu

Atomic mass vs Atomic Weight

Atomic mass = mass of an individual atom

Atomic Weight = average mass of all the isotopes (Carbons atomic wt. = 12.011)Carbon -12 12C Carbon -14 14C

6 protons 6 protons 6 neutrons 8 neutrons 6 electrons 6 electrons

Isotopes

Same element, different mass (due to differing amts. of neutrons)

Stable elements #Protons (p) = #Neutrons(n)

Radioisotopes are the unstable form of the element due to having a larger number of neutrons than protons

Isotope symbols

Uranium -236 236 UWe can always assume that a atom is

neutral unless notedAtomic number tells us the protons (92).

This is many times left off the symbol because it will always be 92 if the element is U.

We assume then that there must be 92 e-The mass number tells us the # neutrons.

Mass Spec

Relative Abundance.

Average atomic weight

Takes the most stable isotopes and their relative abundance to calculate the averages

Ions

Atoms whose electrons do not equal the protons.Metals = cations (+ ions)

Nonmetals = anions ( - ions)Opposites attract to form ionic cpds

(very strong bond=almost always solids with high melting pts)

Fe +3 and Cl -1

Predicting formulas

Review: The atoms always combine so that the number of + balances the number of – charges. Criss Cross method

Polyatomic ions

Groups of atoms with a charge Treat as a single unit. Place ( ) around it if you have more

than l

Ca + 2 and NO3 -1

Naming Ionic

First name is the name of the element written first (cation) unless it’s the Group NH4+1 (ammonium)

Last name is the name of the element written last with an ide ending unless it’s a group (then use the group name) NaCl NaNO3 CaBr Ca(IO3) Ag2S Ag CN

Middle names

Ionic cpds that have a metal with more than one charge/oxidation state need middle names (mainly transitional elements) Fe+2 and Fe +3 Cu +1 and Cu +2 Pb +2 and Pb +4 Sn +2 and Sn +4 Hg +1 (Hg2+2) and Hg +2

Name the following ionic cpds

FeCl3

PbS

CuBr

Cu Br2

Sn (CN)4

Molecular cpds

These are primarily nonmetals elements attached to nonmetal elements due to the sharing of their valence electrons (Also called covalent cpds)

Which of the following are ionic (metal/non) and which are molecular (non/nonmetal) CaBr2 AgF SO2

LiNO3 IF5 CCl4 Cl2 BI3

Naming molecular cpds

First name is the name of the element written first

Last name is the name of the element written last with an ide ending Sulfur= sulfide chlorine = chloride Oxygen = oxide iodine = iodide

Both names have a prefix indicating the number of each atom

Prefixes used on molecular cpds Mono =1 Di =2 Tri =3 Tetra =4 Penta =5 Hexa =6 Hepta=7 Octa=8 Nano =9 Deca =10