In reference to atomicity, argon is:

monoatomic

The correct answer is option 1. monoatomic.

Argon exists as individual atoms and does not form diatomic molecules or larger groups. Therefore, the correct option is Monoatomic.

The term "atomicity" refers to the number of atoms present in a molecule of an element. Argon is a noble gas, and noble gases are known for their monoatomic nature. This means that a single atom of argon constitutes one molecule.

Argon, with the chemical symbol Ar, is part of the noble gas group (Group 18) in the periodic table. Noble gases are characterized by their stable and inert nature, and they exist as single atoms rather than forming diatomic molecules or larger aggregates.

In the case of argon:

Atomicity: Monoatomic

Molecular Structure: Ar

Each molecule of argon consists of a single argon atom, and it does not combine with other atoms to form diatomic (two atoms) or polyatomic (more than two atoms) molecules. The noble gases, including argon, prefer to exist independently as monoatomic species.