How many atoms are in one formula unit of magnesium hydroxide,

Mg (OH),?

5 atoms

Explanation:

A molecule is a particle of a compound or an element that is made up of two or more atoms. A compound is made up atoms from different elements. For example, A compound such as Mg (OH) ₂ is made up of 1 magnesium atom, 2 oxygen atoms and two hydrogen atoms. An element on the other hand is made up of similar atoms. Most elements contain one atom while others such as oxygen and hydrogen are made up of two atoms.