How many neutrons are contained in an iodine nucleus with a mass number of 131?
Group of answer choices
a. 53
b. 127
c. 131
d. 74
e. 78
The correct answer and explanation is:
The correct answer is d. 74.
Explanation:
To find the number of neutrons in an atom, you can use the following formula:
Number of neutrons = Mass number – Atomic number
- Mass number refers to the total number of protons and neutrons in the nucleus.
- Atomic number refers to the number of protons in the nucleus of the atom, which also determines the element.
For iodine (I), the atomic number is 53. This means iodine has 53 protons. The given mass number of iodine is 131.
Now, substitute these values into the formula:
Number of neutrons = 131 (mass number) – 53 (atomic number)
Number of neutrons = 78
So, iodine with a mass number of 131 contains 78 neutrons. The correct option is e. 78.