Question

Derive the molecular formulae of the following compounds stepwise and give their atomicity.

Hydrogen chloride

Answer 1

Derive the molecular formulae of Hydrogen chloride stepwise and give their atomicity:

1. Write the symbols of the elements or the ions forming the compound.
$\mathrm{H}\mathrm{Cl}$

2. Write the valency of each as a superscript to the top right. Ignore the + and - signs of ions.
${\mathrm{H}}^1{\mathrm{Cl}}^1$

3. Interchange the valencies and bring them down diagonally.

4. Write the interchanged valencies as subscripts. Place polyatomic ions in parentheses if the subscript is greater than 1.
${\left(\mathrm{H}\right)}_1{\left(\mathrm{Cl}\right)}_1$

5. Ignore the number 1. Reduce the numbers to the lowest ratio. Write the chemical formula.
$\mathrm{HCl}$

Atomicity: Atomicity is the total number of atoms in a molecule. Molecules may be monoatomic, diatomic, triatomic, or polyatomic depending on the number of atoms.

Thus, the atomicity of HCl is 2.