What happens when you change the number of electrons in an atom

Answer: It becomes an Ion

When an atom has gained or lost electrons (negative charge), it becomes an ion.

In this sense:

Ions are atoms that have gained or lost electrons in their electronic cortex.

If a neutral atom loses electrons, it remains with an excess of positive charge and transforms into a positive ion or cation, whereas if a neutral atom gains electrons, it acquires an excess of negative charge and transforms into a negative ion or anion.

It is then how ions form bonds with other atoms differently depending on the number of electrons they have.