Give the chemical formula for the Hydrogen chloride compound and compute the ratio by mass of the combining elements in it.

Give the chemical formula for the compound Aluminium fluoride and compute the ratio by mass of the combining elements in it.

Give the chemical formula for the compound magnesium sulphide and compute the ratio by mass of the combining elements in it.

State the number of atoms present in the following chemical species: ${\mathrm{CO}}_3^{-2}$.

State the number of atoms present in the chemical species: ${\mathrm{PO}}_4^{3-}$.

State the number of atoms present in the chemical species: ${\mathrm{P}}_2{\mathrm{O}}_5$.

State the number of atoms present in the chemical species: $\mathrm{CO}$