Isotopes class work
1. What is an isotope?
2. What does the mass number represent?
3. What does the atomic number mean and on what document can it be found?
4. Fill in the following table:
Full description
Element
183
74
Mass Number
Protons
Neutrons
81
35
46
W
135
56
Ba
80
36
Kr
Br
Ni
Cu
34
65
134
56
47
194
78
5. Calculate the atomic mass from the following information:
6
3
Li =
6.015123 g/mol
7.42 % abundance
7
3
Li =
7.016005 g/mol
92.58% abundance
60
24
12
Mg
= 23.985045 g/mol
78.90 % abundance
25
12
Mg
= 24.985839 g/mol
10.00 % abundance
26
12
Mg
= 25.982595 g/mol
11.10 % abundance
6. Draw the symbol for an isotope containing 9 protons and 10 neutrons
7. What is the difference between Carbon having a mass number of 12 and an
atomic mass of 12.011?
8. How many neutrons are present in oxygen 17?
9. Draw the symbol for an isotope containing 12 neutrons with a mass number
of 23.
10. What is the mass number of an isotope of Boron containing 6 neutrons?
11. Calculate the atomic mass of Silicone
28
14
Si = 27.976928 g/mol
92.2297 %
29
14
Si = 28.976495 g/mol
4.6832 %
30
14
Si = 29.973770 g/mol
3.0872 %
Isotopes class work Answers
1. What is an isotope? Element with the same # of protons but different
numbers of neutrons
2. What does the mass number represent?
Sum of protons and neutrons
3. What does the atomic number mean and on what document can it be found?
The number of protons, on the periodic table of elements
4. Fill in the following table:
Full description
Element
Mass Number
Protons
Neutrons
W
W
183
74
109
135
56
Ba
Ba
135
56
79
80
36
81
35
Kr
Br
Kr
80
36
44
Br
81
35
46
62
28
65
29
Ni
Ni
62
28
34
Cu
Cu
65
29
36
134
56
Ba
Ba
134
56
78
107
47
Ag
Ag
107
47
60
194
78
Pt
Pt
194
78
116
183
74
5. Calculate the atomic weight from the following information:
6
3
Li =
6.015123 g/mol
7.42 % abundance
7
3
Li =
7.016005 g/mol
92.58% abundance
6.015123 (0.0742) = 0.4463221266
7.016005 (0.9258) = 6.495417429
6.94173955
6.942 g/mol
24
12
25
12
26
12
Mg
Mg
Mg
= 23.985045 g/mol
78.90 % abundance
= 24.985839 g/mol
10.00 % abundance
= 25.982595 g/mol
11.10 % abundance
23.985045 (0.7890) = 18.924200505
24.985839 (0.1000) = 2.4985839
25.982595 (0.1110) = 2.884068045
24.31 g/mol
6. Draw the symbol for an isotope containing 9 protons and 10 neutrons
19
9
F
7. What is the difference between Carbon having a mass number of 12 and an
atomic mass of 12.011?
12 is the protons + neutrons
12.011 is the weighted average of all the isotopes
8. How many neutrons are present in oxygen 17?
9
9. Draw the symbol for an isotope containing 12 neutrons with a mass number
23
11
of 23.
Na
10. What is the mass number of an isotope of Boron containing 6 neutrons?
11. Calculate the atomic mass of Silicone
28
14
29
14
30
14
Si = 27.976928 g/mol
Si = 28.976495 g/mol
Si = 29.973770 g/mol
28.0854142 
92.2297 %
4.6832 %
3.0872 %
28.0854 g/mol
(0.922297) = 25.8030367
(0.046832) = 1.3570272
(0.030872) = 0.92535022
11