Question

A neutral lithium (Li) atom has an atomic number of 3 and a mass number of 7. How many neutrons are in this atom of lithium?

Answer 1

4 Neutrons.

This is right because it is

Answer 2

The atomic number of an atom (Z) is equal to the number of protons.

The mass number of an atom (A) is equal to the number of protons plus the number of neutrons (N), i.e. A = Z + N

Therefore, N = A - Z = 7 - 3 = 4.

So, this neutral lithium atom has 4 neutrons.

Answer: 4.