Foundation of ions.

Ions are charged particles, certain particles can form ions better than others, the reason why some elements want to become ions is because they want to have full outer shells to become stable molecules.

Elements need energy to lose or gain an Electron, so the fewer electrons an element has, the easier it is to lose them, for example, group 1 elements or the Alkali metals can lose their electrons very easily to become -2 ions.
Like group 6, which only needs to lose 2, and group 7, which only needs to gain one, groups 3-5 need to lose 3 electrons, making it harder for them.

We can depict these ions in equations, for example, an equation may look like this:
Na + e-.
This depicts a Sodium atom becoming a Sodium ion.

Cl + e- = Cl-.
This depicts a Chlorine atom becoming a Chlorine ion.

Now something to keep in mind is that when an atom is losing electrons and becoming a positive ion, then we put the electron on the right of the equation.
But if we put the electron on the left of the equation, it means the atom is combining with the electron to.

If an atom loses or gains multiple electrons, like an element like Magnesium, so we would write something like: Mg^2+ + 2e-, so this means Magnesium + 2 electrons.