Here's why:
* Atomic mass number: Represents the total number of protons and neutrons in an atom's nucleus.
* Protons: Positively charged particles found in the nucleus, determining the element's identity.
* Neutrons: Neutral particles found in the nucleus, contributing to the atom's mass but not its charge.
Therefore, subtracting the number of protons from the atomic mass number isolates the number of neutrons.
