Question

An ion is an atom that has had what added or removed?

Answer 1

An ion is an atom that has had one or more electrons added or removed.

Explanation:

Cations are atoms that have lost one or more electrons. Anions are atoms that have gained one or more electrons. The number of electrons lost or gained determines the numeric part of the charge.

Examples of Cations

`"Na"^(+)"` sodium cation

`"Ca"^(2+)"` calcium cation

`"Al"^(3+)"` aluminum cation

Examples of Anions

`"N"^(3-)"` nitride anion

`"O"^(2-)"` oxide anion

`"F"^(-)"` fluoride anion

Answer 2

An electron. Removing one makes a “cation”, adding one makes an “anion”.

Explanation:

An ion is an atom or group of atoms in which the number of electrons is not equal to the number of protons, giving it a net positive or negative electrical charge.

An anion is an ion that is negatively charged, and is attracted to the anode (positive electrode) in electrolysis. A cation has a net positive charge, and is attracted to the cathode (negative electrode) during electrolysis. http://www.diffen.com/difference/Anion_vs_Cation