ACS Chemistry Practice Exam 2025 – The All-in-One Guide to Exam Success!

The term that refers to the different physical forms of an element is "allotropes." Allotropes are essentially variations in the structural arrangements of atoms within an element, which can lead to distinct physical and chemical properties, even though they are composed of the same element. For instance, carbon can exist in several allotropes, including graphite, diamond, and graphene, each exhibiting unique characteristics due to variations in atomic bonding and arrangement.

Isomers, on the other hand, relate to compounds with the same molecular formula but different structures or arrangements of atoms. Compounds refer to substances formed when two or more different elements chemically bond in fixed ratios and structures. Homologues typically describe a series of compounds that differ from each other by a repeating unit, often seen in organic chemistry.

Therefore, "allotropes" accurately captures the concept of an element existing in multiple physical forms.