expression that most accurately describes the basic units of that substance?

Question

categories:
single atoms
diatomic molecules
molecules
formula units 

HgBr2

Xenon

Copper

KMnO4

Ni

C3H8

Ca(OH)2

SO2

H2

Chlorine

CoCL2

Oxygen

Answer 1

Single atoms are those atoms that can exist independently, so Xe fits this since it is one of the noble gases. (Cu and Ni may or may not fit this category. Most likely Cu and Ni are in the formula units category since those metals exist in solid network forms). Diatomic molecules are those molecules that are made of two of the same atom. This includes oxygen, chlorine, and hydrogen gas. Molecules are those that are made of two or more different atoms linked in a covalent bond. The only ones are C₃H₈ (propane) and SO₂. The rest are in ionic bonds, so they are most likely in the formula units category.