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Name:________KEY____________________ Period:________
Isotope Practice
1. Here are three isotopes of an element:
12C
6
13C
6
14C
6
a. The element is: Carbon
b. The number 6 refers to the: Atomic Number
c. The numbers 12, 13, and 14 refer to the different mass numbers
d. How many protons and neutrons are in the first isotope? P: 6
N: 6
e. How many protons and neutrons are in the second isotope? P: 6
f. How many protons and neutrons are in the third isotope? P: 6
N: 7
N: 8
2. Complete the following chart:
atomic #
mass #
# of
protons
# of
neutrons
# of electrons
Potassium-37
19
37
19
18
19
Oxygen-17
8
17
8
9
8
uranium-235
92
235
92
143
92
uranium-238
92
238
92
146
92
boron-10
5
10
5
5
5
boron-11
5
11
5
6
5
Isotope name
3. How do you calculate the mass number of an element?
Mass # = protons + neutrons
4. If an atom has 14 protons, 17 neutrons and 14 electrons, which expression identifies the element?
a. Silicon-14
b. Silicon-28
c. Silicon-31
d. Silicon-17
5. If an atom has 53 protons, 54 neutrons and 53 electrons, which expression identifies the element?
a. Iodine-53
b. Iodine-127
c. Iodine-54
d. Iodine-107
6. If an atom as 24 protons, 32 neutrons, and 24 electrons, which expression identifies the element?
A
7. If an atom has 15 protons, 21 neutrons and 15 electrons, which expression identifies the element?
a.
31
15
P
b.
36
15
P
c.
6
15
P
d.
28
15
P
B
8. How many electrons does the following neutral atom have: Calcium-45?
20 electrons
9. How many electrons does the following neutral atom have: Gallium-72?
31 electrons
10. How many electrons does the following neutral atom have? How do you know?
17 Electrons
11. How many electrons does the following neutral atom have? How do you know?
11 electrons
12. An atom has 32 protons and a mass number of 54. Which of the following is an isotope of this
element?
a. Protons=32, mass number= 54
b. Protons=31, mass number= 53
c. Protons=32, mass number=56
d. Protons=54, mass number=32
13. An atom has 26 protons and a mass number of 52. Which of the following is an isotope of this
element?
a. Protons=25, mass number=52
b. Protons=26, mass number=54
c. Protons=26, mass number=52
d. Protons=52, mass number=26
14. Atoms W, X, Y, and Z have the following nuclear compositions. Which two are isotopes? How do you
know?
45
26
121
24
31 W
12 X 50 Y 12 Z
X and Z because they have the same atomic number but different masses.
15. Atoms W, X, Y, and Z have the following nuclear compositions. Which two are isotopes? How do you
know?
56
52
121
26
W
X
Y
26
26
50
52 Z
W and X because they have the same atomic number but different masses.
16. What is the mass number of the following atoms?
12 amu
13 amu
14 amu
17. Three of the following atoms are isotopes of each other. Which ones are isotopes? Why?
C, D, E are all isotopes because they have the same number of protons but different number of neutrons
and therefore a different mass. This makes them isotopes of each other.
18. What element are the isotopes in the previous problem?
Lithium