What is equal to the mass number minus the atomic number?

The correct answer is based on the relationship between an atom's mass number, atomic number, and its constituent particles. The mass number of an atom is the total number of protons and neutrons in the nucleus, while the atomic number represents the number of protons.

To find the number of neutrons in an atom, you subtract the atomic number from the mass number. This calculation gives you the number of neutrons present, which is a fundamental aspect of nuclear chemistry and physics. Neutrons play a critical role in the stability of the nucleus, while protons affect the element's identity and its chemical behavior.

For example, if an atom has a mass number of 12 and an atomic number of 6, you would perform the calculation: 12 (mass number) - 6 (atomic number) = 6 neutrons. Understanding this relationship is essential for grasping how different elements vary and how isotopes of the same element can exist with differing numbers of neutrons.