What is the term for an atom that is electrically charged as a result of gaining or losing electrons?

An Ion.

Explanation:

The reason is, an ion is a charged particle. The charge can be either a positive charge or a negative charge.

Examples:

Na + : Cation (positively charged ion/particle)

Cl - : Anion (negatively charged ion/particle)

An ion

Explanation:

An ion is a charged atom

Na+

Cl-

K+

SO2-