An atom with an imbalance of electrons to protons is

Answer: Ion

An ion is an atom that is electrically charged by gaining or losing one or more electrons.

To understand it better:

An atom has a nucleus with electrons around it and has a neutral charge. When an electron is added or detached, this atom is electrically charged, that is, it ceases to have a neutral charge and becomes an ion.

In this sense, there are two types of ions:

-Anions: ions negatively charged, by the gain of electrons in the atom.

-Cations: ions positively charged, by the loss of electrons in the atom.