Question

The isotopes of an element X are ${}_z{X}^A,{}_z{X}^{A+1},{}_z{X}^{A+2}$ respectively. What is the ratio of the number of nucleons in these respective isotopes?

• A. 1 : 1 : 1
• B. 1 : 2 : 3
• C. A : (A + 1) : (A + 2)
• D. (A - Z) : ((A + 1) - Z) : ((A + 2) - Z)

Answer 1

The correct option is C

A : (A + 1) : (A + 2)

Protons and neutrons present in the nucleus together are called nucleons.

Also, atomic mass = number of protons + number of neutrons.

So we can say, the ratio of the number of nucleons will be the same as the ratio of atomic masses.

Therefore, ratio of the number of nucleons is $A:(A+1):(A+2)$