Question

The mass number of 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 1

Answer: (A)

Mass number of an element is the total number of protons and neutrons present inside the atomic nucleus of the element. It is represented by A, A is different for different elements. Mass number of a nucleus is sometimes equal to its atomic number,for example in case of hydrogen, number of neutrons= 0.
So, mass number = atomic number.