Question

An isotope of iron has 28 neutrons. If the atomic mass of the isotope is 54, how many protons does it have?
A. 26
B. 28
C. 54
D. 82

Answer 1

26 because you need to do 54-28=26
The atomic mass number is the number of protons AND neutrons together.

Answer 2

An isotope is a varying in the neutrons because the protons NEVERRRR change!!

54 - 28 = 26 

Answer: 26