How many neutrons are present in an atom of zinc-64?

To determine the number of neutrons in an atom of zinc-64, you start with the atomic mass number, which is given as 64. This atomic mass number represents the total number of protons and neutrons in the nucleus of the atom.

Zinc has an atomic number of 30, meaning that it has 30 protons. To find the number of neutrons, you can use the following formula:

Number of neutrons = Atomic mass number - Number of protons.

Substituting in the known values:

Number of neutrons = 64 (atomic mass number) - 30 (number of protons) = 34.

This calculation clearly shows that an atom of zinc-64 contains 34 neutrons, making this the correct answer.