Which prefix indicates a hydrocarbon chain with three carbon atoms?

The prefix that indicates a hydrocarbon chain with three carbon atoms is "Prop-". In organic chemistry, prefixes are used to denote the number of carbon atoms present in the longest continuous chain of a hydrocarbon.

The prefix "Prop-" specifically refers to three carbon atoms. Therefore, any hydrocarbon derivative that has a chain of three carbons would start with this prefix, such as propane (C3H8) for alkanes.

In contrast, "But-" signifies four carbon atoms, "Pent-" signifies five carbon atoms, and "Hex-" signifies six carbon atoms. Understanding these prefixes is essential for naming hydrocarbons correctly and is foundational knowledge in organic chemistry.