Question

Number of neutrons in an atom of \(^{230}_{90}\mathrm{Th}\) is:

• A. 320
• B. 230
• C. 140
• D. 90

Hint:

Number of neutrons = Mass number - Atomic number.

Answer 1

The Correct Option is C

The number of neutrons in a nucleus is given by the difference between the mass number \( A \) and the atomic number \( Z \): \[ \text{Number of neutrons} = A - Z. \] Given the mass number \( A = 230 \) and atomic number \( Z = 90 \), the number of neutrons is: \[ 230 - 90 = 140. \] Hence, the nucleus contains 140 neutrons.