Question

What is the atomicity of phosphorus in its molecule?

Answer 1

Atomicity:

• Atomicity is defined as the number of atoms present in a molecule,
• For example, Water (${\mathbf{H}}_{\mathbf{2}}\mathbf{O}$) contains two atoms of hydrogen ($\mathbf{H}$) and one atom of oxygen ($\mathbf{O}$) and hence its atomicity is 2+1 = 3 i.e. triatomic.

Therefore, atomicity refers to the number of atoms in the molecule.

Phosphorus molecule:

• Phosphorus is a chemical element with the chemical symbol $\mathbf{P}$ and atomic number 15.
• It is non-metal and exists as a solid at room temperature.
• It belongs to the nitrogen family of group 15 of the periodic table, hence having a valency of 3.
• However, because of its large size and little tendency to form triple bonds it completes its octet by sharing valence electrons with three other P atoms which results in the formation of a tetra-atomic ${\mathbf{P}}_{\mathbf{4}}$ molecule.

• Since a molecule of phosphorus contains 4 phosphorus atoms, therefore its atomicity is 4.

Thus, the atomicity of phosphorus in its molecule is 4.