Question

Which is molecular: xenon; argon; barium; iodine; potassium?

Answer 1

This is a difficult distinction to make. Rereading the question, only iodine is a molecular element; it exists as discrete `I_2` molecules

Explanation:

The 2 noble gases are of course mono-atomic; some may be quibble with the distinction, but while these are discrete gaseous particles, they are atomic, not molecular. So, xenon, and argon exist as discrete atoms that exist in the gas phase. Barium and potassium are non-molecular species, which exhibit metallic bonding with no molecular boundaries.

Iodine, however, exists as the `I_2` molecule, and may be considered a molecular element.