Question

The mass number of a nucleus is

Answer 1

The mass number of a nucleus is sometimes more than the atomic number and 
sometimes equal to its atomic number.

Answer 2

The mass number of a nucleus is Sometimes more than and 
sometimes equal to its atomic number.

massnumber= protons + neutrons.

atomic number= Either protons or electrons mass.

So mass number of a nucleus is Sometimes more than and 
sometimes equal to its atomic number