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The Role of Molecules

A molecule is a group of two or more atoms held together by a chemical bond. According to Tech Target, they vary in size from one-atom molecules (such as helium) to hundred- and thousand-molecule chains making up proteins. While molecules are always moving, their rate of speed depends on their states. In a solid state, molecules are the most constrained while in the gaseous state they are the most free. The movement of molecules in the liquid state is somewhere in between the solid and the gas state.

  1. The Facts

    • According to Skwirk, molecules that contain only one atom are called monatomic molecules and those that contain two atoms are called diatomic molecules. Molecules are not limited to being made up of the same element and those that contain two or more different chemically bonded elements are called compounds.

    History

    • According to the History of a Molecule, Antoine-Laurent Lavoisier defined the element as a substance that is not further divisible into smaller substances. During this time, between 1789 and 1803, John Dalton defined an atom as a "small, indestructible and indivisible particle." These definitions allowed for further understanding of chemistry and chemical reactions. In 1809, Joseph-Louis Gay-Lussac, among others, started experimenting with gases by investigating their reactions. He found water is formed by two volumes of hydrogen reacting with one volume of oxygen. Then in 1811, Amendeo Avogadro found that equal volumes of different gases contain the same number of particles (atoms) when held at the same temperature and pressure. As a result, particles that contained more than one atom were eventually named molecules.

    Features

    • According to Skwirk, an important distinction to note between molecules and compounds is that, while not all molecules are compounds, all compounds are molecules. An example of a molecule that is not a compound is one that contains only one element.

    Types

    • The two primary types of compounds are identified on the Skwirk website as ionic and covalent. An ionic compound is one which is held together by an ionic bond. An ionic bond is a type of chemical bond in which the bonded elements either lose or gain electrons. On the other hand, a covalent compound is one which is held together by a covalent bond (a bond in which atoms share the electrons).

    Roles

    • According to Tech Target, molecules have a large range in complexity and size. For example, the element helium has only one atom and is referred to as a one-atom molecule. The most common molecule in the earth's atmosphere is the two-atom oxygen molecule, denoted by O2. Other examples include the three-atom oxygen molecule, O3, found in the ozone layer, in carbon dioxide and in sulfuric acid.

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