Which of the following elements is NOT Diatomic?

(A) Chlorine
(B) Argon
(C) Sulphur
(D) Helium

Choose the correct answer from the options given below:

(B), (C) and (D) only

The correct answer is Option (4) → (B), (C) and (D) only

Analysis of the Elements:

• (A) Chlorine: This is a Diatomic molecule ($Cl_2$). It belongs to the Halogen group, which naturally exists in pairs of atoms.
• (B) Argon: This is a Monoatomic gas ($Ar$). As a Noble Gas, it has a full outer shell of electrons and does not need to bond with another atom to be stable.
• (C) Sulphur: This is a Polyatomic molecule ($S_8$). In its most stable form at room temperature, it consists of eight atoms arranged in a "crown" shape.
• (D) Helium: This is a Monoatomic gas ($He$). Like Argon, it is a Noble Gas and exists as single, isolated atoms.