Question

An atom has a mass number of 24 and 13 neutrons. What is the atomic number of this atom? Express

Answer 1

A=mass number   (protons + neutrons)
Z=atomic number  (protons)
N=number of neutrons.

A=Z+N

Data:
A=24
N=13

Therefore:
24=Z+13
Z=24-13=11

Answer: The atomic number of this atom is 11. (The element is sodium)