What do molecules primarily consist of?

Molecules primarily consist of two or more atoms that are chemically bonded together. This definition highlights the fundamental concept in chemistry that molecules are the smallest units of a chemical compound that retain the properties of that compound. For instance, a water molecule is composed of two hydrogen atoms bonded to one oxygen atom.

Molecules can vary significantly in size; they can be simple, like diatomic molecules such as O₂ (oxygen), or complex, like proteins made up of numerous atoms. The presence of multiple atoms is what distinguishes a molecule from a single atom, which is defined as a basic unit of an element.

While electrons are important components of atoms and play a crucial role in chemical bonding, they do not constitute a molecule by themselves. Similarly, the term "one atom" refers to a single unit of an element, which does not meet the definition of a molecule, and "cells" are much larger structures made up of many molecules and serve as the basic units of life. Therefore, recognizing that the defining characteristic of a molecule is its composition of two or more atoms is essential in understanding molecular chemistry.