What is the smallest part of a compound, consisting of two or more atoms chemically joined together?

The smallest part of a compound that consists of two or more atoms chemically joined together is known as a molecule. A molecule represents the fundamental unit of a chemical compound, retaining the chemical properties of that compound. Molecules can consist of the same type of atom, such as in oxygen gas (O2), or different types of atoms, such as in water (H2O).

An ionic bond refers to the force of attraction between oppositely charged ions but does not denote a distinct unit. An atom is the basic unit of matter, representing a single unit of an element and is smaller than a molecule. A compound is a substance formed when two or more different types of atoms bond together, but it refers to the overall substance rather than the smallest unit of that substance. Hence, a molecule is the correct answer as it specifically describes the smallest identifiable unit comprising multiple atoms joined together.