What rules can you use to tell how many protons, neutrons and electrons make up an atom or ion?

Explanation:

This question appears incomplete, however

The number of protons of an element/atom (atomic number) can be determined by checking for the position of the element on the periodic table. This is because elements are arranged according to there atomic number on the periodic table.

The number of electrons of any element (of a neutral atom) is equal to the number of protons of the same element.

The number of neutrons of an element/atom is determined by subtracting the atomic number of the element from it's mass number. Hence, mass number is the addition of the atomic number and the number of neutrons.

Ions are charged particles that have the same number of protons and neutrons as there parent atoms. Hence, they have different number of electrons when compared to there specific parent/neutral atom.

A negatively charged atom has more electrons than it's original atom. For example, fluoride ion (F⁻) has 10 electrons while fluorine atom has 9 electrons (meaning fluoride ion has one more electron than it's parent fluorine). The increase is dependent on the number "attached" to the charge. A positively charged atom has less electrons than it's original atom. For example, calcium ion (Ca²⁺) has 18 electrons while calcium atom has 20 electrons (meaning the calcium ion has 2 electrons less than it's parent calcium atom). As said earlier, the decrease here is also dependent on the number "attached" to the charge.