1. Example
Example 1: The atom of an element has a mass number of 214 and an atomic number of 82.
a) How many protons and neutrons does it have?
The number of protons is the same as the atomic number, 82.
The number of neutrons
= mass number - atomic number
= 132

2. Example
b) How many electrons are there in the atom if it is electrically neutral?
Because the atom is electrically neutral, the number of electrons equals the number of protons, 82.

3. Example
c) What is the total charge carried in the nucleus of the atom? (Note that the charge carried by an electron is -1.6  C.)
The charge carried by a proton is equal and opposite to the charge carried by an electron.
Total charge carried by the nucleus
= 82  (1.6  C)
=  C
End