NEET Physics Atomic Physics NEET PYQ-Atomic Physics

The mass number of a nucleus is:                                                              [AIPMT 2003]

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

Correct Answer: A

Solution :
Mass number = Atomic number + Number 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.