Question

multiple choice question
what term describes a one - atom ion, such as $ce{mg^{2+}}$ or $ce{cl^-}$?

$circ$ monatomic ion
$circ$ single ion
$circ$ simple ion
$circ$ univalent ion

Explanation:

A one-atom ion is defined as a monatomic ion, where "mono-" means single/one, and "-atomic" refers to atom. The other options do not match this definition: "simple ion" is not the precise scientific term, "single ion" is vague, and "elemental ion" is not the standard classification for this concept.

Answer:

A. monatomic ion