Question

question 3
____ is defined as the number of protons plus the number of neutrons
atomic number
nuclear number
ionic number
isotopic number
mass number

Explanation:

The mass number of an atom is calculated by adding the number of protons and neutrons in its nucleus. The atomic number is just the number of protons. Other terms like nuclear number, ionic number, isotopic number are not standard terms for this sum.

Answer:

E. Mass number