A molecule is the tiniest unit in a chemical element or compound that includes chemical compositions. Molecules are made up of atoms that are joined by chemical bonds. These bonds are formed by the exchange and sharing of electrons between atoms. The atoms of such elements easily combine with other elements to form molecules. Oxygen and chlorine are two examples of such elements. Some elements’ atoms are difficult to connect with those of other elements. Neon and argon are two examples. Water is made up of two hydrogen atoms and one oxygen atom, while carbon dioxide is made up of one carbon atom connected to two oxygen atoms. Sulfuric acid is made up of two hydrogen atoms, one sulfur atom, and four oxygen atoms.
Molecules come in a wide range of sizes and complexity. Helium is a molecule with only one atom. Two atoms of the same element make up certain molecules. For example, is the most common oxygen molecule found in the earth’s atmosphere; it contains two oxygen atoms. Under certain conditions, however, oxygen atoms link into triplets, generating the molecule ozone.
Hundreds or even thousands of atoms come together in chains that can reach significant lengths in some compounds, particularly proteins. Liquids holding such molecules can act strangely at times. A liquid, for instance, may continue to move out of a flask after part of it has been emptied, even after the flask has been placed upright.
Molecules are constantly moving. They are firmly packed together in solids and liquids. The mobility of molecules in a solid can be compared to fast vibrations. In a liquid, molecules can freely move about in a slithering pattern. The density of molecules in a gas is often lower than that of the same chemical composition in a liquid or solid, and they move even more rapidly than in a liquid. The speed of molecular motion rises as the comparative temperature rises for a certain molecule in a given state (solid, liquid, or gas).