Multiple choice

Mass number is the sum of ________ and ________ present in an atom.

  1. protons and electrons

  2. electrons and neutrons

  3. protons and neutrons

  4. electrons and positron

Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The mass number of an atom is defined as the total number of protons and neutrons in its nucleus. Electrons have negligible mass compared to protons and neutrons.