What is the formula to determine the neutron number in an atom?

The formula used to determine the number of neutrons in an atom is derived from the relationship between atomic mass, atomic number, and neutron count. The atomic mass (which is approximately equal to the mass number) represents the total number of protons and neutrons in the nucleus. The atomic number, on the other hand, indicates the number of protons present in the nucleus of the atom.

To find the number of neutrons, you subtract the atomic number (the number of protons) from the atomic mass (the total number of protons and neutrons). This gives you the equation:

Number of Neutrons = Atomic Mass - Atomic Number.

This formula allows you to calculate how many neutrons are present in an atom, which can vary between different isotopes of the same element, while the atomic number remains constant for a given element. Thus, using this reasoning, the correct method for determining the neutron count in an atom is by subtracting the atomic number from the atomic mass.