How does sulphur has atomicity 8, when its valence electrons are 6 like oxygen- ie even 2 sulphur atoms can share a pair of electrons and achieve the octet rule, why it should involve 8 atoms
Atomicity is defined as the number of atoms in a molecule of that element.
For example Oxygen molecule consists of two atoms of oxygen chemically bonded to each other.
So the atomicity of oxygen is 2 and therefore it is a diatomic gas.
Some solid elements like phosphorus and sulphur have more than two atoms in their molecules.
For example Phosphorus exists as P4 molecules.
Each phosphorus molecule consists of four atoms of phosphorus. So its atomicity is 4 and is tetra-atomic.
Sulphur molecules consist of eight atoms per molecule.
Its atomicity is 8 and so it is polyatomic.