Post on 06-May-2018
CHEM 111 Fall 2017
Table of Contents
(italicized entries indicate worksheets and extra practice problems)
Periodic Table
Calculator usage in General Chemistry
Algebra worksheet (and answers)
Chapter 0 notes
Significant figures worksheet (and answers)
Unit simplification worksheet (and answers)
Chapter 1 notes
1A 8A
1
H
1.00794
2A
3A
4A
5A
6A
7A
2
He
4.00260
3
Li
6.941
4
Be
9.01218
<––––––
<––––––
<––––––
Atomic number
Elemental symbol
Atomic mass
5
B
10.811
6
C
12.0107
7
N
14.0067
8
O
15.9994
9
F
18.99840
10
Ne
20.1797
11
Na
22.98977
12
Mg
24.305
3B
4B
5B
6B
7B
<------------8B ----------->
1B
2B
13
Al
26.98154
14
Si
28.0855
15
P
30.97376
16
S
32.066
17
Cl
35.4527
18
Ar
39.948
19
K
39.0983
20
Ca
40.078
21
Sc
44.9556
22
Ti
47.88
23
V
50.9415
24
Cr
51.994
25
Mn
54.938
26
Fe
55.847
27
Co
59.9332
28
Ni
58.6934
29
Cu
63.546
30
Zn
65.39
31
Ga
69.723
32
Ge
72.61
33
As
74.9216
34
Se
78.96
35
Br
79.904
36
Kr
83.80
37
Rb
85.4678
38
Sr
87.62
39
Y
88.9059
40
Zr
91.224
41
Nb
92.9064
42
Mo
95.94
43
Tc
(98)
44
Ru
101.07
45
Rh
102.9055
46
Pd
105.42
47
Ag
107.868
48
Cd
112.41
49
In
114.82
50
Sn
118.710
51
Sb
121.757
52
Te
127.60
53
I
126.9045
54
Xe
131.29
55
Cs
132.9045
56
Ba
137.33
57
La
138.9055
72
Hf
178.49
73
Ta
180.9479
74
W
183.85
75
Re
186.207
76
Os
190.2
77
Ir
192.22
78
Pt
195.08
79
Au
196.966
80
Hg
200.59
81
Tl
204.383
82
Pb
207.2
83
Bi
208.98
84
Po
(209)
85
At
(210)
86
Rn
(222)
87
Fr
(223)
88
Ra
226.0254
89
Ac
(227)
104
Rf
(265)
105
Db
(268)
106
Sg
(271)
107
Bh
(272)
108
Hs
(270)
109
Mt
(276)
110
Ds
(281)
111
Rg
(280)
112
Cn
(285)
113
Nh
(285)
114
Fl
(289)
115
Mc
(288)
116
Lv
(293)
117
Ts
(294)
118
Og
(294)
58
Ce
140.12
59
Pr
140.9077
60
Nd
144.24
61
Pm
(145)
62
Sm
150.36
63
Eu
151.965
64
Gd
157.25
65
Tb
158.9253
66
Dy
162.50
67
Ho
164.9303
68
Er
167.26
69
Tm
168.9342
70
Yb
173.04
71
Lu
174.967
90
Th
232.0381
91
Pa
231.0359
92
U
238.029
93
Np
237.0482
94
Pu
(244)
95
Am
(243)
96
Cm
(247)
97
Bk
(247)
98
Cf
(251)
99
Es
(252)
100
Fm
(257)
101
Md
(258)
102
No
(259)
103
Lr
(262)
Calculators in General Chemistry
During exams in this class you will use only CASIO fx-260solar calculators. These are simple, scientific
calculators that will be more than sufficient to perform any calculations you will encounter in general
chemistry. Below are images of the two models of calculators (light keys and dark keys):
In the display of each is the number 6.626 10-34. Notice how the exponential numbers (10-34) leave out
the “10”—this part is assumed. So how do you input an exponential value into one of these calculators?
Use the EXP key (see the black arrow in the figures below).
If you want to use the number 6.626 10-34 in a calculation, you simply type 6.626 34 . The
means that you will raise 10 to some power. Notice how you would type in 109 or 1 109. If you want to
type in this number you would type 1 9. If you type 10 9 the calculator would translate this as
10 109, which would be 1010—your calculation would be off by a whole order of magnitude!!
Lastly, here are some displays of numbers from a typical calculation (1.92697736 1025). The Casio
returns 10 digits, plus the power of 10. Each calculator actually keeps more digits in its memory than is
displayed on the screen. In general chemistry, 10 figures will be more than enough digits for your
calculations.
Although these calculators are simple, they are powerful, too. They have
1. memory functions,
2. a way to retype a number if you put in a wrong digit,
3. take the reciprocal of a number,
4. calculate square roots and cube roots quickly, and
5. nested functions (i.e., use parentheses to separate parts of a calculation).
EXP +/- EXP
EXP EXP
1. Hit the SHIFT key, then MR to
put the number to the memory. Hit
MR to recall the number from memory
2. Hit this arrow
key to backspace
4b. Hit SHIFT,
then +/- to take
the cube root
4a. To take the square
root, hit the SHIFT key,
followed by x2
5. These keys allow you to perform
functions in parentheses
3. Hit SHIFT and the ---)] key to take
the reciprocal of a number
Algebra basics review sheet
Solve each of the following for x (that is, provide an answer where x = <number>). Do not use a calculator.
If you cannot easily work the problems on this sheet—WITHOUT A CALCULATOR, you most likely do not have the math
skills necessary for successful completion of this course. It is strongly recommended that you take more math to boost those
skills, then enroll in general chemistry.
1. 5.6 = 1.6x + 2
2. x
1612
3. 5.49
5)32(
x
4. (1000)(4.022) = (25.00)(x)
5. –4.33 – x = -2.55
6. x = 15 × 3 + 12 – 2 × 3 + 2
16
4
12 – 6 × 6 + 7
7. 50100
78 x
8. 41
x
9.
5.5
11
x
10. 123
34 xx
Algebra answers:
1. 2.25
2. 1.33333
3. 40.1
4. 160.88
5. -1.78
6. 33
7. 39
8. 0.25 (or 4
1 )
9. 5.5
10.
17
6
Chapter 0 page 1 of 8
CHEM 111-Chapter 0
Chemical Tools: Experimentation and
Measurement
Chapter 0 Problems: 1-55, 58-83, 85-91, 92a
Is chemistry a:
(a) cult?
(b) science?
(c) religion?
(d) passing fad?
How do we define chemistry?
The Scientific Method
1st step-make an observation
2nd step-form a hypothesis
3rd step-conduct an experiment
If experimental conclusions don't match the hypothesis, which option should you choose?
(1) reject hypothesis or (2) reject experimental data
Theory: Complex hypothesis or set(s) of hypotheses/laws that have been repeatedly tested and not
shown to be wrong. Differs from a hypothesis because it is a broad ranging explanation (explains a
broad set of phenomena)
Science: A way of knowing about the physical universe (as opposed to other ways of "knowing”, eg.
belief, intuition). Utilizes processes of testing and experimentation to support or reject explanations
(hypotheses and theories) and descriptions of phenomena in the physical universe.
Chapter 0 page 2 of 8
Measurements (Numbers and Units)
To write large and small numbers we will use scientific notation (#.## × 10x)
EX. 425,000 can be written as:
Another way to express very large and very small quantities is to use prefixes with the metric system
Table of Metric Prefixes
Prefix Symbol Value Example tera- T 1012 1,000,000,000,000 trillion 1 terameter (1 Tm) = 1012 m
giga- G 109 1,000,000,000 billion 1 gigameter (1 Gm) = 109 m
mega- M 106 1,000,000 million 1 megagram (1Mg) = 106 g
kilo- k 103 1,000 thousand 1 kilogram (1 kg) = 103 g
hecto- h 102 100 hundred 1 hectogram (1 hg) = 100 g
deka- da 101 10 ten 1 dekaliter (1 daL) = 10 L
-- -- -- -- -- --
deci- d 10-1 0.1 tenths 1 deciliter (1 dL) = 0.1 L
centi- c 10-2 0.01 hundredths 1 centiliter (1 cL) = 0.01 L
milli- m 10-3 0.001 thousandths 1 milliliter (1 mL) = 0.001 L
micro- μ 10-6 0.000 001 millionths 1 micrometer (1 μm) = 10-6 m
nano- n 10-9 0.000 000 001 billionths 1 nanometer (1 nm) = 10-9 m
pico- p 10-12 0.000 000 000 001 trillionths 1 picometer (1 pm) = 10-12 m
femto- f 10-15 0.000 000 000 000 001 quadrillionths 1 femtosecond (1 fs) = 10-15 s
Note that some abbreviations are capitalized while others are not.
Capitalization must be preserved to avoid confusion with other abbreviations.
Science uses a standardized system of units (the Systeme International d'Unites, SI) to describe physical
quantities. This list shows the “fundamental units” ● Mass-kilogram (kg) ● Length-meter (m) ● Light intensity-candela (cd)
● Time-second (s) ● Electric current-amp (A)
● Temperature-kelvin (K) ● Amount of substance-mole (mol) (1 mole is 6.022 1023 things)
A bit more on fundamental units
The SI unit for mass is kg, but it is more common to use the g or mg.
Mass and weight are not synonymous.
Chapter 0 page 3 of 8
The SI unit for length is the meter, but it is very common to use cm, mm, and nm
KNOW THIS: 1 inch = 2.54 cm (exactly)
Three different scales in common use Temp scale Freezing point, water Boiling point, water
Fahrenheit 32 °F 212 °F
Celsius 0 °C 100 °C
Kelvin 273 K 373 K
To convert between Celsius and Fahrenheit:
32CF59oo
EX. “Room temperature” is 25 °C, what is the temp in °F?
To convert from °C to K: K = °C + 273.15
EX. The flashpoint of a liquid is the lowest temperature at which the vapors will support combustion.
The flashpoint of octane (C8H18) is ~288 K. If the temperature is 12 °C (54 °F), would an arsonist be
able to use pure octane to start a fire?
Derived units
Combining fundamental units allows expression of other quantities ● Area (length2) ● Energy (mass × length2/time2) ● Acceleration (length/time2)
● Volume (length3) ● Density (mass/length3) ● Force (mass × length/time2)
● Speed (length/time) ● Frequency (1/time) ● Pressure (mass/length/time2)
Volume is defined as the amount of space an object occupies; it has no fundamental unit—but if
we had to choose the closest SI equivalence, it would be cubic meters (m3).
Chapter 0 page 4 of 8
Energy is made of units involving mass, length, and time (mass × length2/time2)—what would
this be using SI units?
Other energy units: calorie, Calorie
Density is a ratio of mass to volume and is independent of the amount of material, though it is
temperature dependent
)L
g:used(also
cm
g
mL
g
volume
massDensity
3
Densities of common materials Liquid water at ~4 °C, 1.00 g/mL (KNOW THIS!!)
Solid ice at 0 °C, 0.917 g/cm3
Mercury: 13.55 g/mL
Iron: 7.87 g/cm3
NaCl: 1.54 g/cm3
Oxygen gas: 1.43·10-3 g/mL = 1.43 g/L
EX. With the high price of gold, investors need to be sure of what they are buying (or selling). If gold
has a density of 19.32 g/cm3, is a 25.0 g sample with a volume of 1.3 cm3 pure or adulterated gold?
SIGNIFICANT FIGURES
How many digits are appropriate to report in your answer? You should always report the correct number
of significant figures (or significant digits). The number of “sig figs” is equal to all of the certain digits,
plus one uncertain digit.
EX. A measurement of 2.74 cm MEANS the object is definitely between 2.7 and 2.8 cm. The 0.04 is the
best guess.
2.74 cm REALLY MEANS 2.74 ± 0.01 = the range 2.73 to 2.75 cm (3 sig figs)
EX. 313.6 g REALLY MEANS the value has a range of 313.5 g to 313.7 g (313.6 ± 0.1) (4 sig figs)
Chapter 0 page 5 of 8
How many sig figs are in these numbers?
2.04
423.05
0.00630
1.2 × 10 3
1.20 × 10 3
1.200 × 10 3
1200
1200.
Mathematical operations with significant figures Addition/Subtraction: Line up the decimal, perform the operations, drop those digits that are undefined
EX. 18.43 + 1.27304 EX. 44.89 + 0.002
Note: It is possible to gain or lose sig figs with addition and subtraction operations.
EX. 85.86+ 26.41 EX. 70.6 - 67.6
Multiplication/Division: Round the answer to the number of sig figs that are found in the original
number with the fewest sig figs
EX. 5.30 × 90.51146
EX. 027.0
38.52 EX. 3025.286.31
987.77.44
Rounding
If the digit to the right of where you are rounding is < 5, truncate
If the digit to the right of where you are rounding is > 5, round up
If the digit to the right of where you are rounding is = 5, round up if it will make the final digit
even, otherwise, truncate.
EX. Round the following to the underlined digit:
1.234 =
1.236 =
1.235 =
1.245 =
1.24500000000000001 =
Chapter 0 page 6 of 8
Only round at the END of your calculation Why do we follow these rules?
(1) The “rounding-with-5”-rule avoids number bias. The chance of rounding up or down is 50/50.
(2) It’s systematic. If everyone follows these rules, everyone should get the same answer—every time.
Precision is improved!
Precision -how close measurements are to each other
Accuracy -how close measurements are to the true value.
Unit Conversion
1 simple formula:
(original quantity) x (conversion factor) = (equivalent quantity with new units)
(original quantity) x (conv. factor 1) x (conv. factor 2) x (conv. factor 3)... = equiv. quant
EX. How many eggs do you have if you have 2 dozen eggs?
EX. Given the information in the table, if you have 3 A's, how many B's do you have? How many E's do
you have? 1A = 4B
6B = 5C
7C = 4.8D
2D = 4.76E
EX. Convert 19.5 m to km.
EX. Convert 55.90 g to μg.
EX. The largest wingspan of a bird on record is of a wandering albatross at 11 ft 11 inches. How many
meters is this?
Chapter 0 page 7 of 8
EX. Convert 4.79 km to yards.
EX. My dog, a Pembroke Welsh corgi, sheds a LOT of hair. One estimate is that
she sheds 174.3 pounds per year. If 13,497 hairs has a mass of 5.000 g, how
many days until 9.00 106 hairs are shed?
EX. The sun consumes 5.8 108 metric tons of hydrogen atoms each second. If 1 hydrogen atom is
1.67372 10-24 grams, how many moles of hydrogen are being used in 1.000 hour?
EX. To break bone, a bullet typically needs to travel 213 feet per second. Would a bullet traveling at
120. miles per hour be fast enough?
EX. The lowest lethal concentration of ozone reported is 2.7 g/m3. If a room was measured to have a
concentration of 13.65 mg/ft3, would the concentration be high enough to kill?
Chapter 0 page 8 of 8
EX. In arson investigations the heat of combustion is an important property telling how much energy is
given off when something burns. Which has a greater heat of combustion: methane (3.7 104 kJ/m3) or
gasoline (1.93 104 Btu/lb). Note that 1 Btu = 1055 J (not exact) and for gasoline, 0.70 g = 1 mL.
EX. The Glaister equation,
death since hours1.5
F)in (body temp98.4 0
, is used to estimate time of death by
measuring body temperature. What is the body temperature, in Celsius, if the body is found 435 minutes
after death?
Significant Figures Worksheet
Remember the rules for sig figs and keep track of significant versus non-significant digits, but underlining the non-significant
ones. Also, DO NOT ROUND any number, until the very end of the calculation. Doing so may cause your result to be
different than the answer.
1. 4.993 + 0.743 + 1.22
2. 6.1 + 123.51 + 16.216
3. 12.43 6.7 99.220
4. 16.47 - 2.47
5. 23.71 + 11.29
6. 6.731103 + 2.114105
7. 6.73110-3 + 2.11410-5
8. 125.0 12.0
9. 9083.17
31.1241.66
10. 8.128.16
4.3214.12
11. 00.1000.10
0.10841.9
12. 00.10000.10
00.10841.9
13. m 1
nm 10
cm 100
m 1
in 1
cm 2.54
ft 1
in 12ft 6.763
9
Significant Figures Worksheet Answers
1. For addition and subtraction, line up the numbers by the decimal place, perform the operation, then determine where digits
are undefined.
2. For multiplication and division, use the value with the fewest significant figures and apply that number to the product or
quotient.
3. If you have mixed operations (addition and multiplication, for instance), you must use the order of operations and keep
track of the significant digits AT EACH STEP.
4. DO NOT ROUND any number until the very end of your calculation. With a calculator, this shouldn’t be difficult since
most calculators have storage locations to keep numbers (often up to 15 digits long).
1. 4.993 + 0.743 + 1.22
4.993 (4 sig figs)
0.743 (3 s. f.)
+ 1.22_ (3 s. f.)
¯¯¯¯¯¯¯
6.956 = 6.96 (3 sig figs)
2. 6.1 + 123.51 + 16.216
6.1_ _ (2 s. f.)
123.51_ (5 s. f.)
+ 16.216 (5 s. f.)
¯¯¯¯¯¯¯
145.826 = 145.8 (4 s. f.)
3. 12.43 6.7 99.220 = 8263.14082 = 8.3 103
4. 16.47 - 2.47
16.47 (4 s.f.)
- 2.47 (3 s.f.)
¯¯¯¯¯¯¯
14.00 (4 s.f.)
5. 23.71 + 11.29
23.71 (4 s. f.)
+ 11.29 (4 s. f.)
¯¯¯¯¯¯¯
35.00 (4 s.f.)
6. 6.731103 + 2.114105
Line up values by decimal place, to the same power of 10!
6731 (4 s. f.)
+ 211400 (4 s. f.)
¯¯¯¯¯¯
218131 = 2.181 105 (4 s. f.)
7. 6.73110-3 + 2.11410-5
0.006731_ _ (4 s. f.)
+ 0.00002114 (4 s. f.)
¯¯¯¯¯¯¯¯¯¯¯
0.00675214 = 0.006752 or 6.752 10-3 (4 s. f.)
8. 125.0 12.0 = 1500 = 1.50103 (3 s. f.)
(4 s. f.) (3 s. f.)
9. 9083.17
31.1241.66 =
f. s. 6
f. s. 4
9083.17
10.54 = 3.020945595
= 3.021 (4 s. f.)
10. 8.128.16
4.3214.12
=
f. s. 2
f. s. 3
0.4
336.339 = 98.334
= 98 (2 s. f.)
11. 00.1000.10
0.10841.9
=
f.) s. (5 00.100(3s.f.) 0.10
(1s.f.) 591.0
= f.) s. (5 00.100(1s.f.) 5901.0
= -1.59 (1 s. f.) = -2 (1 s. f.)
12. 00.10000.10
00.10841.9
=
f.) s. (5 00.100(4s.f.) 00.10
(2s.f.) 915.0
= f.) s. (5 00.100(2s.f.) 9015.0
= -1.59 (2 s. f.) = -1.6 (2 s. f.)
13. m 1
nm 10
cm 100
m 1
in 1
cm 2.54
ft 1
in 12ft 6.763
9
= 2061362400 = 2.061 109 (4 s. f.)
Note in #13, each conversion factor has an infinite
number of significant figures, the result is limited by the
first value (6.763 ft).
CHEM 111 Unit simplification worksheet
As you progress though chemistry, unit conversions and formulas that involve units will become a very important aspect to
understanding the material. In the worksheet below, determine the unit(s) that result from each calculation. Numbers have
been omitted for clarity, just focus on the units. Simplify derived units to the fundamental unit counterparts, but don’t include
conversions unless they are given in the problem.
(a) kg×g
kg×
cm
g
(b) (J×s)(m
s⁄ )
nm×
nm
m
(c) (J×s)
kg×𝑚𝑠⁄ note that 1 J = 1 kg•m2/s2
(d) 1
(1
g)
(e) g
(1
cm)
×cm
(f) (J×s)×m/s
kJmol⁄
×1
mol×
kJ
J
(g) (J×s)
mg×kmh⁄
(h) (J×s)
mg×kmhr
⁄× mg
g× g
kg× km
m× hr
s
Answers:
(a) cm
(b) J (i.e., kgm2/s
2)
(c) m
(d) g
(e) gcm2
(f) m
(g) kg×𝑚2/s
mg×𝑘𝑚ℎ⁄
=kg×𝑚2×h
s×mg×km (these are nonsensical units, but the point is to see what
units cancel and which don’t)
(h) m×hr2/s
2
Chapter 1 page 1 of 9
CHEM 111-Chapter 1
The Structure and Stability of Atoms
Chapter 1 Problems: 1-57, 59-107, 110-113
What is the nature of matter?
Empedocles (492-432 BCE) is credited with categorizing matter as mixtures of four elements: earth, air,
fire, and water. (Plato (427-347 BCE) later added a fifth element: the ether.)
First "atomic" theory proposed by Democritus (460-370 BCE)
Democritus’ ideas were not entirely correct
atoms ARE breakable
atoms don't come in an infinite number of shapes
atoms don't come in an infinite number of types
Element: a fundamental substance that can't be chemically changed or broken down into anything
simpler
Good News: There are only 118! (currently)
Other Good News: We’ll focus primarily, but not exclusively, on ~90!!
Elemental symbols: 1 or 2 letter abbreviations of the full name. First letter is ALWAYS capitalized,
second letter is NEVER capitalized. Note elements 114 and 116...
Most elemental symbols are derived from the English name of the element, but not all...
Chapter 1 page 2 of 9
In 1869 Russian chemist Dmitri Mendeleev derived an ingenious way to arrange the elements according
to how they react. Elements in a column had similar reactivities. This was called the “periodic law” and
was the precursor to our modern periodic table.
Elements can be divided into different sections based on location or properties
1. Metals (most elements)
Properties: shiny, silvery in color (exceptions?), solid at room temperature (exceptions?), malleable
(able to be hammered into thin sheets), sectile (able to be cut into thin sheets), ductile (able to be drawn
into wires), good conductor of heat, and good conductor of electricity. (Hardness is NOT a property of
metals.)
EX. Aluminum (Al): used in airplanes, cola cans, cooking foil
Iron (Fe): used for structural materials (cars, buildings, desks)
Gold (Au): used in dentistry, jewelry, computer contacts
2. Non-metals (17 elements)
Properties: May be solid, liquid, or a gas at room temperature (depends on the element), variety of
colors, if solid will be brittle (thus, not malleable, sectile, or ductile), very poor conductors of heat, and
very poor conductors of electricity.
EX. Nitrogen (N): ~78% of air
Oxygen (O): ~21% of air
Argon (Ar): ~1% of air
Chlorine (Cl): yellow gas, used to disinfect water (drinking and pools)
Bromine (Br): red liquid, used to disinfect hot tub water
Iodine (I): purple solid, used as a topical disinfectant
3. Metalloids (aka semimetals) (7 elements-B, Si, Ge, As, Sb, Te, At)
Properties: Solid at room temperature, brittle, conduct heat and electricity better than nonmetals, but
not as well as metals.
Silicon (Si): finds many uses in computer circuitry and solar cells
Boron (B): used in control rods for nuclear reactors
Rows versus columns.
Elements in a group react in similar ways.
Some Special Groups
1-alkali metals-Li, Na, K, Rb, Cs, Fr
2-alkaline earth metals-Be, Mg, Ca, Sr, Ba, Ra
15-pnictogens (nitrogen group)-N, P, As, Sb, Bi
16-chalcogens (oxygen group)-O, S, Se, Te, Po
17-halogens-F, Cl, Br, I, (At)
18-noble gases-He, Ne, Ar, Kr, Xe, Rn
11 or 1B-coinage metals-Cu, Ag, Au
Four Classifications of properties
Physical property: Characteristics that can be determined without changing the chemical makeup of the
sample
Chemical property: Characteristics that DO change the sample (the sample undergoes a chemical
reaction).
See table 1.3, pg 32
Chapter 1 page 3 of 9
Extensive property: A property that DOES depend on the amount of sample
Intensive property: A property that is independent of the amount of sample.
Examples of extensive properties: mass, volume, length/width, etc.
Examples of intensive properties: temperature (boiling point, melting point, too), hardness, conductivity
(heat and electrical), color, etc.
Some Chemical History Next big step in atomic theory: Robert Boyle (1627-1691)
-clearly defined the term element and determined that when different elements combined a new
substance called a compound was formed.
Next big step: Antoine Lavoisier (1743-1794)
Law of Mass Conservation: Matter is neither created nor destroyed in chemical reactions
Major chemical principle #2: Joseph Proust (1754-1826)
Law of definite proportions: Different samples of a pure chemical substance always contain the same
proportion of elements by mass.
John Dalton (1766-1844) proposed two important concepts:
Law of Multiple Proportions: Elements can combine in different ways to form different chemical
compounds, but their mass ratios must be simple whole numbered multiples
Dalton’s Theory of Matter (1) Elements are made of tiny particles called atoms
(2) Each element is characterized by the mass of its atoms. Atoms of the same element have the same
mass, but atoms of different elements have different masses.
(3) Chemical combinations of elements to make different substances occur when atoms join together in
small, whole number ratios.
(4) Chemical reactions only rearrange the way atoms are combined; the atoms themselves are not
destroyed.
Chapter 1 page 4 of 9
Atomic structure Radioactivity proved atoms were made of smaller components
Experiments with beta-rays (beta particles, -particles)
J. J. Thomson (1856-1940) and others used cathode ray tubes to study a beam of particles that flowed
toward a positive wire. These were called electrons. By careful manipulation of magnetic and electric
fields, Thomson calculated the charge-to-mass ratio of the electron (Figure 2.3):
-e/m = -1.758820 108 C/g
R. A. Millikan (1868-1953) designed the “oil drop experiment” to measure the electron's charge (Figure
2.4). If Millikan’s result was -e=-1.602176 10-19 C, then what is the mass of an electron?
Early atomic models
Democritus
Dalton
Plum Pudding
In 1911, Ernest Rutherford blew all of these models away with one "simple" experiment.
Chapter 1 page 5 of 9
What IS the nucleus?
Protons
Symbol: p or p+
has a +1 charge
mass of 1.672622 10-24 g (this is ~1836 times the mass of an electron)
Neutrons (theorized by Rutherford, but not discovered until 1933)
Symbol: n
no charge
mass of 1.674927 10-24 g
In a neutral atom, the number of protons = the number of electrons
ATOMIC NUMBER (Z): the number of protons in the nucleus of an atom
This is the defining characteristic of an element!!!
Atoms of the same element CAN have different numbers of neutrons
Chapter 1 page 6 of 9
For instance, there are three types of hydrogen atoms
“protium” = 1 proton, 0 neutrons
“deuterium” = 1 proton, 1 neutron
“tritium” = 1 proton, 2 neutrons (unstable and radioactive)
ALL contain 1 proton, but different numbers of neutrons. What effect does this have on the mass of
each kind of hydrogen?
ISOTOPES: atoms with identical atomic numbers, but different numbers of neutrons
MASS NUMBER (A): Total number of n and p+ in an atom
A = Z + n
EX. How many protons, neutrons, and electrons are in the following?
K3919
3Au199
79 124Sn4-
p+ = p+ = p+ =
n = n = n =
e- = e- = e- =
Different elements have different masses AND even atoms of the SAME element can have different
masses if there are multiple isotopes
Problem: Dealing with the mass (in g, kg, mg, ng, etc.) of individual atoms is inconvenient.
Solution: Use the "amu"-the atomic mass unit
1 amu = 1/12 of 12C, 1 amu = 1.66054 10-24 g (not exact)
so...12C has a mass of 12.000000 amu
Note that atoms have just one mass listed on the periodic table—the so-called atomic mass—even if
there are mutliple isotopes.
ATOMIC MASS (ATOMIC WEIGHT): the weighted average of all the isotopic masses of an
element's naturally occurring isotopes
EX. Chlorine consists of two isotopes, 35Cl (mass = 34.9688527 amu, % abund = 75.77%) and 37Cl (mass = 36.9659026 amu, % abund = 24.23%). What is the atomic mass?
Note the close relationship between an atom’s mass in amu and its mass number...
Note: Some atoms only have one isotope, thus the atomic mass IS the mass of those particular atoms.
Chapter 1 page 7 of 9
Be, 9.01218 amu
F, 18.99840 amu
Na, 22.98977 amu
These atomic masses give you a way to convert between the number of atoms and the mass.
EX. What mass (in amu) is 5000. titanium atoms? What is this mass in grams?
Better yet, because of a wise choice in how the amu is defined, there is a link to the value of the mole.
EX. How many atoms are in 12.0107 g of C?
So 1 carbon atom = 12.0107 amu, but 6.022 1023 (an Avogadro’s number, i.e., 1 mole) of carbon = 12.0107 g
The atomic mass, expressed in units of grams instead of amu, is called the molar mass.
EX. 1 Fe atom = ____________ amu; 1 mole of Fe = _______________ grams
EX. 1 Mg atom = ____________ amu; 6.022 1023 Mg atoms = _______________ grams
EX. How many moles of Hg are present in a medical thermometer which contains 2.5 g of Hg?
EX. If a rebar has 9.941 g of Fe per centimeter of length, how many Fe atoms are there in 2.50 feet of
rebar?
Nuclear Chemistry
Chapter 1 page 8 of 9
Alchemy was the magical belief that elements could become a totally new element (i.e., transmutation).
Once chemical principles were discovered, this old way of thinking was discarded...until radioactivity
was discovered in the 1890s.
Like chemical reactions, nuclear reactions are written with a specific format:
Reactants Products
and the reactions must be balanced—with respect to Z and A. Reactions are balanced by ADDING the
correct species to either the reactant or product side—NEVER use a subtraction in a reaction!!
ALSO: DO NOT use an equals sign (=) between reactants and products, use an arrow ()
Nuclear reactions don’t concern themselves with charges on ions—focus on what’s happening to the
nucleus.
EX. The spontaneous break up of 235U can lead to multiple products
U23592 Tc105
43 + Ag12647 + He4
2
Types of Radioactive Decay
Gamma (γ) radiation-results from emission of high energy light from the nucleus—often left out of
nuclear reactions because it doesn’t change the number of protons or neutrons
EX. The cobalt-58 nucleus can exist (temporarily) in an unstable state, which gives off γ radiation to
become more stable.
*58
27Co Co58
27 + γ
In almost all nuclear reactions, gamma radiation results, even if other particles are emitted.
Alpha (α) radiation-results from emission of a helium nucleus ( 242 He , just written as He4
2 or 4
2α)
EX. Write the reaction for the alpha emission of americium-241, an element found in smoke alarms.
Beta (β-) radiation-results from emission of an electron from the nucleus ( eor β 01-
01-
)
How is this electron created? Note the Law of Charge Conservation: The net charge of an isolated
system remains constant. Charge can be created and destroyed, but only in positive-negative pairs.
EX. Technetium-99 is used as a radioactive tracer in medicine. What products result when it undergoes
β-decay?
What does this say about the stability of neutrons?
Chapter 1 page 9 of 9
Positron (β+) emission-results from the emission of an antimatter electron (positron) from the nucleus ( β01
)
How is the positron created?
EX. “PET scans” are used in medicine to locate tumors and monitor certain types of brain activity.
Sugar molecules containing fluorine-18, a known positron emitter, are taken by the patient—what is the
β01
emission reaction?
What ultimately happens to the positron?
Electron capture (E. C.)-process whereby an electron is sucked into the nucleus and converts a proton
into a neutron
EX. While chromium has stable isotopes with mass numbers of 50, 52, 53, and 54, chromium-51 is
unstable and undergoes electron capture—what is the reaction?
Other nuclear reactions are also possible, but not discussed in the book. Atoms may emit protons,
neutrons, a proton/neutron pair (deuteron), and other subatomic particles, but these are rare.
Nuclei can also be “encouraged” to react by bombardment of nuclei with neutrons, protons, or even
larger atoms.
The heavy atoms recently created had large nuclei that were smashed together at enormous speeds. This
is the reaction that created the first copernecium atoms.
Pb20882 + Zn70
30 Cn278112