Question

Which one of the following elements exists as a monoatomic molecule?

• A. Oxygen
• B. Phosphorus
• C. Sulphur
• D. Argon

Answer 1

The correct option is D

Argon

The explanation for the correct option

(D) Argon

Classifications of molecules

• The elements that have just one atom are referred to as monoatomic molecules.
• The elements that have two atoms are referred to as diatomic molecules.
• The elements that have three atoms are referred to as triatomic molecules.
• The elements that have four atoms are referred to as tetraatomic molecules.
• Polyatomic molecules are elements with more than two atoms bound together by a covalent bond.

Argon

• Argon $\left(\mathrm{Ar}\right)$ is a monoatomic.

Explanation for incorrect options

(A) Oxygen

• Oxygen $\left({\mathrm{O}}_2\right)$ is a diatomic molecule.

(B) Phosphorus

Phosphorus $\left({\mathrm{P}}_4\right)$ is a tetra-atomic molecule.

(C) Sulphur

• Sulphur $\left({\mathrm{S}}_8\right)$ is a polyatomic molecule.

Therefore, the correct option is (D) Argon.