A molecular of phosphorus is

Analyze the question: The question asks about the atomicity of a phosphorus molecule, meaning how many atoms are joined together in one molecule of phosphorus.

Explain the concept: Atomicity is the number of atoms in one molecule of an element. Common examples:

• Monoatomic: noble gases (He, Ne, Ar)
• Diatomic: H₂, O₂, N₂, Cl₂
• Triatomic: O₃ (ozone)
• Tetraatomic: P₄ (white phosphorus)
• Octaatomic: S₈ (sulphur)

Solution:

1. Phosphorus (in its common form, white phosphorus) does not exist as single atoms or pairs.
2. Four phosphorus atoms bond together in a tetrahedral arrangement, with each atom bonded to the other three.
3. The molecular formula is therefore P₄.
4. Since there are 4 atoms per molecule, phosphorus is tetraatomic.

Nitrogen, which is in the same group, is diatomic (N₂) because it forms strong triple bonds. Phosphorus atoms are larger and form weaker π bonds, so they prefer the P₄ tetrahedral structure.

Answer: The correct option is C. tetraatomic.

Tip: Remember the atomicity sequence with the examples: "He (1), O₂ (2), O₃ (3), P₄ (4), S₈ (8)." WASSCE often asks about P₄ and S₈, so memorize these two.