Question
The mass number of a nucleus is
A.
sometimes equal to its atomic number
B.
sometimes less than and sometimes more than its atomic number
C.
always less than its atomic number
D.
always more than its atomic number
Answer :
sometimes equal to its atomic number
Solution :
Mass number = No. of protons + No. of neutrons
For example, in case of hydrogen
Number of neutrons = 0
Thus, mass number = atomic number
Hence, sometimes the atomic number is equal to the mass number.