HOMEWORK – DUE Thursday 8/31/17 Read for Thursday: Chapter 3 section 2-3 HOMEWORK – DUE Thursday 8/31/17 BW 2b (Bookwork): CH 2 #’s 10, 11, 17, 19, 23, 25, 37 – 43 (odd) WS 3 (Worksheet): (from course website) Lab Next Wednesday/Thursday EXP 2 – dry lab Prelab – flash cards

Atoms vs. Ions 1 p+ – 1 e – 47 p+ – 47 e– Atoms are NEUTRAL!!!!! This means that they have zero charge #p+ = #e- 1 p+ – 1 e – 47 p+ – 47 e– When #p+ = #e-, the atom has no charge and is neutral

Atoms vs. Ions Atoms can gain or lose e- to form IONS ANY charged particle is called an ion Losing e- gives POSITIVELY charge

Charge!!! + – 11 p+ = 11 p+ 10 e– = 11 e– = 10 e– – 1+ – + When an atom LOSES electrons 10 e– = 11 e– = 10 e– – 1+ Before After Na  Na+ + e– Na Na  Na+ – +

Atoms vs. Ions Atoms can gain or lose e- to form IONS ANY charged particle is called an ion Losing e– gives POSITIVELY charge Called cations Usually formed from metals Gaining e- gives a NEGATIVELY charged ion

Charge!!! 16 p+ = 16 p+ 16 e– = 18 e– = 18 e– – 2– + – When an atom GAINS electrons 16 e– = 18 e– = 18 e– – 2– Before After S  S2– + 2e– S S  S2– WRONG!! S S + 2e–  S + 2e–  S2– –

Atoms vs. Ions Atoms can gain or lose e- to form IONS ANY charged particle is called an ion Losing e- gives POSITIVELY charge Called cations Usually formed from metals Gaining e- gives a NEGATIVELY charged ion Called anions Usually formed from non-metals

My Atom Broke Subatomic Particles Nucleus Neutrons – no No charge # can vary from atom to atom

Mass of no about equal to mass of p+ Do each of these atoms have the same mass? Isotopes: Atoms having the same atomic number, but different atomic masses

A E S 16 Z Atomic symbols Mass number = # p+ + # no Symbol of element Atomic number

32 A S E 16 Z 33 S 16 32 S 16 34 S 16 36 S 16 Shorthand: Sulfur-33

Give the atom notation for the following: 1) an atom with 82 p+ and 126 no 2) an atom of iron with 28 no and 26 e- 3) an atom of element 29 having 34 no and 27 e- 208 82 p+ + 126 no = Pb 82 54 Fe 26 63 2+ Cu 29

Information from the Periodic Table (atomic number) 20 = = 40.08 amu (atomic mass) (atomic number) 8 = = 16.00 amu (atomic mass)

GO TO NOTES INSERT

Atomic Masses Measured in the unit amu 35Cl = 34.9689 amu Stands for atomic mass unit Defined as 1/12th the mass of a 12C atom 35Cl = 34.9689 amu 50V = 49.9472 amu 79Br = 78.9183 amu Are these what the P.T. say?

Weighted Averages “regular” average (mean): add all numbers and divide by how many there are. what is the average of 11, 8, 23, 18? weighting factors

Weighted Averages “weighted” average: multiply all values by their weighting factor what is the average of 11, 8, 8, 8, 8, 8, 8, 8, 23, 18?

Weighted Averages weighting factors must add to 1 (100%)