Practice!

Sample Problem

Th-232 has an atomic number of 90. How many protons, electrons, and neutrons are in neutral Th-232?

Number of protons =

Number of electrons =

Number of neutrons =

Solution

The mass number of Th-232 is 232.

Number of protons = atomic number = 90

Number of electrons = number of protons = 90

Number of neutrons = mass number – number of protons = 232 – 90 = 142