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A space-filling model of the diatomic molecule dinitrogen, N 2. Diatomic molecules (from Greek di- 'two') are molecules composed of only two atoms, of the same or different chemical elements. If a diatomic molecule consists of two atoms of the same element, such as hydrogen (H 2) or oxygen (O 2), then it is said to be homonuclear.
The study of molecules by molecular physics and theoretical chemistry is largely based on quantum mechanics and is essential for the understanding of the chemical bond. The simplest of molecules is the hydrogen molecule-ion, H 2 +, and the simplest of all the chemical bonds is the one-electron bond.
Diatomic molecules consist of a bond between only two atoms. They can be broken into two categories: homonuclear and heteronuclear. A homonuclear diatomic molecule is one composed of two atoms of the same element. Examples are H 2, O 2, and N 2. A heteronuclear diatomic molecule is composed of two atoms of two different elements.
The exact atomicity of metals, as well as some other elements such as carbon, cannot be determined because they consist of a large and indefinite number of atoms bonded together. They are typically designated as having an atomicity of 2. The atomicity of homonuclear molecule can be derived by dividing the molecular weight by the atomic weight.
Triple bonds are stronger than the equivalent single bonds or double bonds, with a bond order of three. The most common triple bond is in a nitrogen N 2 molecule; the second most common is that between two carbon atoms, which can be found in alkynes. Other functional groups containing a triple bond are cyanides and isocyanides.
Two or more atoms can combine to form molecules. Some elements are formed from molecules of identical atoms, e. g. atoms of hydrogen (H) form diatomic molecules (H 2). Chemical compounds are substances made of atoms of different elements; they can have molecular or non-molecular structure.
In addition to electronic quantum states, molecules have internal degrees of freedom corresponding to rotational and vibrational motion. At appreciable temperatures, many of these new motional modes are excited, resulting in constant motion as seen above. Molecular physics is the study of the physical properties of molecules and molecular dynamics.
The following tables list molecules that have been detected in the interstellar medium or circumstellar matter, grouped by the number of component atoms. Neutral molecules and their molecular ions are listed in separate columns; if there is no entry in the molecule column, only the ionized form has been detected. Designations (names of ...