Q. 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
Explanation
(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.
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.