Homonuclear molecule

 ( Sets Of Chemical Elements ) 

In chemistry, homonuclear molecules, or elemental molecules, or homonuclear species, are composed of only one Chemical element. Homonuclear molecules may consist of various numbers of . The size of the molecule an element can form depends on the element's properties, and some elements form molecules of more than one size. The most familiar homonuclear molecules are diatomic molecules, which consist of two atoms, although not all diatomic molecules are homonuclear. Homonuclear diatomic molecules include hydrogen (), oxygen (), nitrogen () and all of the . Ozone () is a common triatomic homonuclear molecule. Homonuclear tetratomic molecules include arsenic () and phosphorus ().

are different chemical forms of the same element (not containing any other element). In that sense, allotropes are all homonuclear. Many elements have multiple allotropic forms. In addition to the most common form of gaseous oxygen, , and ozone, there are other allotropes of oxygen. Sulfur forms several allotropes containing different numbers of sulfur atoms, including diatomic element, triatomic, and octatomic () forms, though the first three are rare. The element carbon is known to have a number of homonuclear molecules, including diamond and graphite.

Sometimes a cluster of atoms of a single kind of metallic element is considered a single molecule. "How many gold atoms make gold metal?".

• Heteronuclear molecule
• Homonuclear diatomic molecules
• Homonuclear triatomic molecules