Homonuclear molecule
Encyclopedia
Homonuclear molecules, or homonuclear species, are molecule
s composed of only one type of element
. Homonuclear molecules may consist of various numbers of atom
s, depending on the element's properties. Some elements form molecules of more than one size. Noble gas
es rarely form bonds, so they only have one atom. The most familiar homonuclear molecules are diatomic
, meaning they consist of two atom
s, though not all diatomic molecules are homonuclear. Homonuclear diatomic molecules include hydrogen
(H2), oxygen
(O2), nitrogen
(N2) and all of the halogen
s. Oxygen, in addition to its diatomic form, also forms the homonuclear triatomic molecule, ozone (O3). Homonuclear tetratomic molecules include arsenic
(As4) and phosphorus
(P4). Sulfur
forms diatomic, hexatomic and octatomic
homonuclear molecules (S2, S6, S8), though the first two are rare. The element carbon
is known to have a number of homonuclear molecules, the best known being buckminsterfullerene
or "buckyball" (C60)
Molecule
A molecule is an electrically neutral group of at least two atoms held together by covalent chemical bonds. Molecules are distinguished from ions by their electrical charge...
s composed of only one type of element
Chemical element
A chemical element is a pure chemical substance consisting of one type of atom distinguished by its atomic number, which is the number of protons in its nucleus. Familiar examples of elements include carbon, oxygen, aluminum, iron, copper, gold, mercury, and lead.As of November 2011, 118 elements...
. Homonuclear molecules may consist of various numbers of atom
Atom
The atom is a basic unit of matter that consists of a dense central nucleus surrounded by a cloud of negatively charged electrons. The atomic nucleus contains a mix of positively charged protons and electrically neutral neutrons...
s, depending on the element's properties. Some elements form molecules of more than one size. Noble gas
Noble gas
The noble gases are a group of chemical elements with very similar properties: under standard conditions, they are all odorless, colorless, monatomic gases, with very low chemical reactivity...
es rarely form bonds, so they only have one atom. The most familiar homonuclear molecules are diatomic
Diatomic
Diatomic molecules are molecules composed only of two atoms, of either the same or different chemical elements. The prefix di- means two in Greek. Common diatomic molecules are hydrogen , nitrogen , oxygen , and carbon monoxide . Seven elements exist in the diatomic state in the liquid and solid...
, meaning they consist of two atom
Atom
The atom is a basic unit of matter that consists of a dense central nucleus surrounded by a cloud of negatively charged electrons. The atomic nucleus contains a mix of positively charged protons and electrically neutral neutrons...
s, though not all diatomic molecules are homonuclear. Homonuclear diatomic molecules include hydrogen
Hydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...
(H2), oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
(O2), nitrogen
Nitrogen
Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...
(N2) and all of the halogen
Halogen
The halogens or halogen elements are a series of nonmetal elements from Group 17 IUPAC Style of the periodic table, comprising fluorine , chlorine , bromine , iodine , and astatine...
s. Oxygen, in addition to its diatomic form, also forms the homonuclear triatomic molecule, ozone (O3). Homonuclear tetratomic molecules include arsenic
Arsenic
Arsenic is a chemical element with the symbol As, atomic number 33 and relative atomic mass 74.92. Arsenic occurs in many minerals, usually in conjunction with sulfur and metals, and also as a pure elemental crystal. It was first documented by Albertus Magnus in 1250.Arsenic is a metalloid...
(As4) and phosphorus
Phosphorus
Phosphorus is the chemical element that has the symbol P and atomic number 15. A multivalent nonmetal of the nitrogen group, phosphorus as a mineral is almost always present in its maximally oxidized state, as inorganic phosphate rocks...
(P4). Sulfur
Sulfur
Sulfur or sulphur is the chemical element with atomic number 16. In the periodic table it is represented by the symbol S. It is an abundant, multivalent non-metal. Under normal conditions, sulfur atoms form cyclic octatomic molecules with chemical formula S8. Elemental sulfur is a bright yellow...
forms diatomic, hexatomic and octatomic
Octatomic element
An octatomic element is a chemical element that, under standard conditions for temperature and pressure is stable, when in a configuration of eight atoms grouped together. The canonical example is sulfur, S8, but also octaoxygen is known....
homonuclear molecules (S2, S6, S8), though the first two are rare. The element carbon
Carbon
Carbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds...
is known to have a number of homonuclear molecules, the best known being buckminsterfullerene
Buckminsterfullerene
Buckminsterfullerene is a spherical fullerene molecule with the formula . It was first intentionally prepared in 1985 by Harold Kroto, James Heath, Sean O'Brien, Robert Curl and Richard Smalley at Rice University...
or "buckyball" (C60)