Interpret the number of moles of oxygen atoms in $PO_{4}^{3-}$ ion.

Compute the number of ions present in $5.85 \, g$ of sodium chloride.

$(i)$ Name the body which approves the nomenclature of elements and compounds.
$(ii)$ The symbol of sodium is written as $Na$ and not as $S$. Give reason.
$(iii)$ Name one element which forms diatomic and one which forms tetraatomic molecules.

Mass of one atom of oxygen is

Give the formulae of the compounds formed from the following sets of elements:
$(a)$ Calcium and fluorine
$(b)$ Hydrogen and sulphur
$(c)$ Nitrogen and hydrogen
$(d)$ Carbon and chlorine
$(e)$ Sodium and oxygen
$(f)$ Carbon and oxygen

Write the chemical formulae and names of the compounds formed by the combination of:
$(i)$ $Fe^{3+}$ and $SO_{4}^{2-}$
$(ii)$ $NH_{4}^{+}$ and $CO_{3}^{2-}$