The combining capacity of an atom is known as its valency. The number of bonds that an atom can form as part of a compound is expressed by the valency of the element.
Monovalent
An atom, ion, or chemical group with a valence of one, which thus can form one covalent bond is called monovalent.
Examples
Atoms that are monovalent are
- Hydrogen
- Lithium
- Sodium
- Chlorine
Divalent
An atom, ion, or chemical group with a valence of two, is called divalent.
Examples
Atoms that are divalent are
- Beryllium
- Oxygen
- Magnesium
- Sulphur
Trivalent
An atom, ion, or chemical group with a valence of three, is called trivalent.
Examples
Atoms that are trivalent are
- Boron
- Nitrogen
- Aluminium
- Phosphorous
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