Identifying Elements with Diatomic Atomicity

Atomicity refers to the number of atoms that make up a molecule of an element. Some elements exist as single atoms (monatomic), while others exist as molecules containing two (diatomic), three (triatomic), or more atoms (polyatomic). The question asks us to find which among the given options has diatomic atomicity.

Let's look at the common forms of the given elements:

• Argon (Ar): Argon is a noble gas. Noble gases exist as single atoms and are therefore monatomic. Its atomicity is 1.
• Phosphorus (P): Phosphorus typically exists as molecules containing four atoms, known as white phosphorus (P₄). It can also exist in other forms like red phosphorus or black phosphorus which are polymeric. Its common atomicity is 4.
• Sulphur (S): Sulphur commonly exists as molecules containing eight atoms, in a ring structure (S₈). Its common atomicity is 8.
• Nitrogen (N): Nitrogen is a gas at room temperature and atmospheric pressure. It exists as molecules containing two nitrogen atoms chemically bonded together. The chemical formula for nitrogen gas is N₂. Thus, nitrogen has diatomic atomicity.

Based on the natural state of these elements, Nitrogen is the one that exists as diatomic molecules.

Elements that are commonly diatomic include Hydrogen (H₂), Nitrogen (N₂), Oxygen (O₂), Fluorine (F₂), Chlorine (Cl₂), Bromine (Br₂), and Iodine (I₂). These are often remembered by the acronym "BrINClHOF".

Comparing this with the options, Nitrogen (N) fits the definition of a diatomic element because it exists as N₂ molecules.