molecule

Smallest configuration of an element or compound that can exist independently. One molecule is made up of a group of atoms held together by covalent or ionic bonds. Several non-metal elements exist as molecules. For example, hydrogen atoms, at room temperature, do not exist independently. They are bonded in pairs to form hydrogen molecules. A molecule of a compound consists of two or more different atoms bonded together. For example, carbon dioxide is made up of molecules, each containing one carbon and two oxygen atoms bonded together. The molecular formula is made up of the chemical symbols representing each element in the molecule and numbers showing how many atoms of each element are present. For example, the formula for hydrogen is H₂, and for carbon dioxide is CO₂. Molecules vary in size and complexity from the hydrogen molecule to the large macromolecules of proteins. In general, elements and compounds with molecular structures have similar properties. They have low melting and boiling points, so that many molecular substances are gases or liquids at room temperatures. They are usually insoluble in water and do not conduct electricity even when melted.