First Sci-Fi Movie Released (1902) Read for Thursday
Chapter 3: Sections 3-4 HOMEWORK – DUE Thursday 9/3/15
HW-BW 2 (Homework Bookwork) #’s 1-7 all, 14, 19, 21, 23, 36, 47-50 all, 57, 59-66 all, 81, 82, 113, 114, 116, 127, 132
HW-WS 2 (Homework Worksheet) (from course website) HOMEWORK – DUE Tuesday 9/8/15
HW-BW 3.1 (Bookwork) CH 3 #’s 3, 4, 11-24 all, 26, 27 HW-WS 3 (Worksheet) (from course website)
HOMEWORK – DUE Thursday 9/10/15 HW-BW 3.2 (Bookwork) CH 3 #’s 41, 45, 48, 56-61 all, 68, 70, 72, 73, 78, 79,
85, 88, 95, 96, 104, 119, 124 HW-WS 4 (Worksheet) (from course website)
Lab Wednesday/Thursday EXP #2- PRELAB!!!!
Atoms vs. IonsAtoms can gain or lose e- to form IONS
ANY charged particle is called an ionLosing e- gives POSITIVELY charge
Called cationsUsually formed from metals
Gaining e- gives a NEGATIVELY charged ion
16 e- =
Charge!!!
When an atom GAINS electrons
SS S2-S S2- + 2e-
Before After
SS + 2e- S + 2e- S2-
WRONG!!
18 e- = 18 e–
16 p+ = 16 p+
––2
Atoms vs. IonsAtoms can gain or lose e- to form IONS
ANY charged particle is called an ionLosing e- gives POSITIVELY charge
Called cationsUsually formed from metals
Gaining e- gives a NEGATIVELY charged ionCalled anionsUsually formed from non-metals
My Atom Broke
Subatomic ParticlesNucleus
Neutrons – no
No charge# can vary from atom to atom
16p+
16no16p+
17no
16p+
18no16p+
20no
16p+
16no16p+
17no
16p+
18no16p+
20no
16p+
20no
16p+
18no
16p+
17no
16p+
16no
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
Atomic symbols
EA
Z
Symbol of
element
Atomic number
Mass number
= # p+ + # no
S16
16p+
20no
16p+
18no
16p+
17no
16p+
16no
3216
16p+
20no
16p+
18no
16p+
17no
16p+
16noA
Z
S
E3216S
3316S
3416S
3616S
Shorthand: Sulfur-33
S-3636S
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-
20882Pb
5426Fe
6329Cu
82 p+ + 126 no =
+2
Information from the Periodic Table
= 40.08 amu (atomic mass)
= 16.00 amu (atomic mass)
(atomic number) 20 =
(atomic number) 8 =
20Ca40.08
8O
16.00
Atomic MassesMeasured in the unit amu
Stands for atomic mass unitDefined as 1/12th the mass of a 12C atom
35Cl = 34.9689 amu50V = 49.9472 amu79Br = 78.9183 amuAre these what the P.T. say?
All Isotopes are NOT Created EqualWeighted averages
285 5145
2
All Isotopes are NOT Created Equal
Atomic mass is a WEIGHTED average of isotopes
HUH?? Final Quiz300 20Possible
You earned 285 5
average =
(93.75%) (6.25%)
(score1 x weight1) + (score2 x weight2) = grade
14545.3%
320
(285(285 x 0.9375)(285 x 0.9375) + (5(285 x 0.9375) + (5 x 0.0625) =(285 x 0.9375) + (5 x 0.0625) = 267.5267.5
83.6%320
All Isotopes are NOT Created EqualWeighted averagesAn equation (oh crap)
35Cl = 34.9689 amuAbundance = 75.77%
37Cl = 36.9659 amuAbundance = 24.23%
These must be the only 2 isotopes... Why?
isotope mass 1 abundance 1 isotope mass 2 abundance 2 average atomic mass
35Cl = 34.9689 amuAbundance = 75.77%
37Cl = 36.9659 amuAbundance = 24.23%
isotope mass 1 abundance 1 isotope mass 2 abundance 2 average atomic mass
34.9689x 0.7577+ 36.9659x 0.2423= 35.45amu
Where have I seen this before?
Periodic Table gives AVERAGE ATOMIC MASS in amu!!
=0.7577
=0.2423
All Isotopes are NOT Created Equal
isotope mass 1 abundance 1 isotope mass 2 abundance 2 average atomic mass+
78.90% of all magnesium is 24Mg 23.985 amu
10.00% of all magnesium is 25Mg 24.986 amu
11.10% of all magnesium is 26Mg 25.983 amu11.10%
100.00% 23.985 0.7890 18.92
24.986 0.1000 2.499
25.983 0.1110 2.884
24.303
= 24.30 amu
A Problem!What is the average atomic mass of magnesium?
DO NOT use “normal” averagesIf asked for two percent-abundances, use:
If asked for ANYTHING else:
Isotopes Calculation Summary
isotope mass 1 abundance 1 isotope mass 2 abundance 2 average atomic mass+
1 isotope mass 1 X isotope mass 2 X average atomic mass
A Problem!Thallium has 2 isotopes, and . has a
mass of 202.973 amu and has a mass of 204.974 amu. What are the percent abundances of each of the isotopes?
1 isotope mass 1 X isotope mass 2 X average atomic mass
1 202.973 amu X 204.974 amu X average atomic mass 1 202.973 amu X 204.974 amu X 204.37 amu
202.973 amu X 204.974 amu 204.974 amu X 204.37 amu
202.973 amu X 204.974 amu X 0.604 amu
2.001 amu X 0.604 amu
X=0.302 Abundance 1 = 30.2% Abundance 2 = 69.8%
20381Tl 205
81Tl 20381Tl
20581Tl
A Problem!Bromine has 2 isotopes, and . has a
mass of 78.9193 amu and has a mass of 80.9163 amu. What are the percent abundances of each of the isotopes?
1 isotope mass 1 X isotope mass 2 X average atomic mass
7935Br 81
35Br 7935Br
8135Br
1 78.9193 amu X 80.9163 amu X average atomic mass 1 78.9193 amu X 80.9163 amu X 79.909 amu
78.9193 amu X 80.9163 amu 80.9163 amu X 79.909 amu
78.9193 amu X 80.9163 amu X 1.0073 amu
1.997 amu X 1.0073 amu
X=0.5044 Abundance 1 = 50.44% Abundance 2 = 49.56%
Percent CompositionHow much of each element makes up a compound
part you are talking about
100 = %everything present
[number of moles of element] [molar mass of element]100 = %
molar mass of compound
total mass of element
100 = %molar mass of compound
element
100 = %compound
