Question

Write down the formulae of magnesium hydroxide.

Answer 1

Hint: Atomic number of magnesium is 12. Valency of Magnesium is 2. In magnesium hydroxide, Magnesium is bonded to two hydroxyl groups. The atomic number of oxygen is 8. Valency of oxygen is 2. An atomic number of hydrogen is 1. Valency of hydrogen is 1. Magnesium donates two electrons and oxygen accepts two electrons to complete its octet and acquire stability.

Complete step by step solution:
-Atomic number of magnesium is 12. Electronic configuration of magnesium is $1s^{2}2s^{2}2p^{6}3s^2$. It belongs to group 2 in the periodic table also known as alkaline earth metals.
-Valency of magnesium is 2. The oxidation number of magnesium is +2 as it donates two electrons.
-In magnesium hydroxide, magnesium is bonded to two hydroxyl groups so the chemical formula of magnesium hydroxide is $Mg{(OH)}_2$.
-Structural Formula of magnesium hydroxide is

-As the atomic mass of magnesium is 24, the atomic mass of oxygen is 16 and the atomic mass of hydrogen is 1.
So molecular mass or molar mass of magnesium hydroxide is 58.
-Magnesium hydroxide is prepared by reacting a solution of magnesium salts with alkaline water which forms a precipitate of solid magnesium hydroxide.
-Commercially, seawater is treated with lime that is calcium hydroxide.
Magnesium hydroxide is a weak base. It has low solubility with water. It is a common component of an antacid such as milk of magnesia.
-In hydroxide ion, oxygen and hydrogen atoms are bonded by a covalent bond.
so the chemical formula of magnesium hydroxide is $Mg{(OH)}_2$.

Note: In magnesium hydroxide, Magnesium is bonded to two hydroxyl groups. The Valency of magnesium is two. Oxygen has charge of -2 and hydrogen has charge of +1, so overall charge on hydroxide ion is -1 and charge on magnesium ion is +2, so two hydroxyl groups are bonded to magnesium to form the electrically neutral molecule. Magnesium hydroxide is known as milk of magnesia as it has a milk-like appearance.it is used as a laxative.