1. 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

2. 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

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

4. 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+ – +

5. 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

6. 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– –

7. 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

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

11. 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

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

13. 32 A S E 16 Z 33 S 16 32 S 16 34 S 16 36 S 16 Shorthand: Sulfur-33

14. 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 no = Pb 82 54 Fe 26 63 2+ Cu 29

15. Information from the Periodic Table
(atomic number) 20 =
= amu (atomic mass)
(atomic number) 8 =
= amu (atomic mass)

16. GO TO NOTES INSERT

17. 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 = amu
50V = amu
79Br = amu
Are these what the P.T. say?

18. 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

19. 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?

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