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CHEMISTRY I
Isotopes Worksheet
1. Atoms of the same element with a different number of neutrons are called ____________________.
2. The two sub-atomic particles that determine the mass of an atom are __________ and __________.
3. _____________ is the only particle in the nucleus that can be changed in number without changing
the element.
Complete the Following Table:
Symbol
Isotope Name
Atomic
Number
# Protons
# Neutrons
59
Mass
Number
# Electrons
86
65
91
Phosphorus-32
38
79
26
57
Tin-120
47
78
Given the Following Information, Calculate the Average Atomic Mass:
4.
Isotope
Uranium-238
Uranium-235
Uranium-234
5. Element X-46
Element X-49
Element X-50
Molar Mass
238.1g/mol
235.0 g/mol
234.0 g/mol
Natural Abundance
99.28%
.71%
0.0054%
46.2 g/mol
48.9 g/mol
50.1 g/mol
24%
57%
19%
6. There are three isotopes of Neon…Neon-20, Neon-21, and Neon-22. Which of these isotopes is most
abundant in nature, and how do we know?
7. Which of the following 3 mystery elements are actually isotopes of each other (circle the two)?
57
25
X
57
28
X
59
28
X
8. What is the element above (with the two isotopes)?