The mass number of a nucleus is

Options

A. Always equal to its atomic number
B. Sometimes more than and sometimes equal to its atomic number
C. Always less than its atomic number
D. Always more than its atomic number

Answer

B

Explanation

Only (b) is correct
only in the case of `""_1H^1` (hydrogen nucleus) the mass number of the nucleus =its atomic number .
Z =1 and A =1
For deutron `""_1H^2 , A gt Z` or for other nuclei `""_ZX^A, A gt Z` .