Question

What is the empirical formula for magnesium hydroxide (milk of magnesia)?

Answer 1

Hint: Empirical formula of any compound is defined as the simplest whole number ratio of various atoms present in a compound. It is different from the exact quantity or numbers of atoms present, as it is the simplest form of those quantities of atoms. Magnesium is a metal placed in group 2 of the periodic table.

Complete answer:
Empirical formula for any compound is the representation of it in its simplest whole number ratio. The chemical formulas of compounds are written in such a manner, as to compensate the valences present in the atoms of the element. For instance, one negative charge of any ion cannot form a compound with an element having a charge of positive two. Therefore, those negative ions are taken in a quantity of two, and the whole numbers are written as subscript for their respective amounts.
We have been given magnesium hydroxide, which is also called milk of magnesia. The respective formula for magnesium is, Mg and that of hydroxide is OH. Magnesium is present in the group 2 of the periodic table, so it has a valency of 2, which means it loses 2 electrons to form compounds. On the other hand, hydroxide has a 1 negative charge, so magnesium will lose 2 electrons, which will be compensated by 2 atoms of hydroxide ion. Therefore the empirical formula of magnesium hydroxide will have 1 magnesium ion and 2 hydroxide ions as,
Magnesium hydroxide = $Mg{{(OH)}_{2}}$
Hence the empirical formula for magnesium hydroxide is $Mg{{(OH)}_{2}}$.

Note:
Milk of magnesia which is magnesium hydroxide is used as an antacid, as it is a base and neutralizes the acid formed in the stomach. Milk of magnesia is given to a person when a condition of acidity arises. $Mg{{(OH)}_{2}}$is an ionic compound as it is formed by transfer of electrons.