Nonmetals Definition and Properties

A nonmetal is simply an element that does not display the properties of a metal. It is not defined by what it is, but by what it is not. It doesn't look metallic, can't be made into a wire, pounded into shape or bent, doesn't conduct heat or electricity well, and doesn't have a high melting or boiling point.

The nonmetals are in a minority on the periodic table, mostly located on the right-hand side of the periodic table. The exception is hydrogen, which behaves as a nonmetal at room temperature and pressure and is found on the upper left corner of the periodic table. Under conditions of high pressure, hydrogen is predicted to behave as an alkali metal.

Nonmetals on the Periodic Table

The nonmetals are located on the upper right side of the periodic table. Nonmetals are separated from metals by a line that cuts diagonally through the region of the periodic table containing elements with partially filled p orbitals. The halogens and noble gases are nonmetals, but the nonmetal element group usually consists of the following elements:

hydrogen
carbon
nitrogen
oxygen
phosphorus
sulfur
selenium

The halogen elements are:

fluorine
chlorine
bromine
iodine
astatine
Possibly element 117 (tennessine), although most scientists think this element will behave as a metalloid.

The noble gas elements are:

helium
neon
argon
krypton
xenon
radon
element 118 (oganesson). This element is predicted to be a liquid but is still a nonmetal.

Properties of Nonmetals

Nonmetals have high ionization energies and electronegativities. They are generally poor conductors of heat and electricity. Solid nonmetals are generally brittle, with little or no metallic luster. Most nonmetals have the ability to gain electrons easily. Nonmetals display a wide range of chemical properties and reactivities.

Summary of Common Properties

High ionization energies
High electronegativities
Poor thermal conductors
Poor electrical conductors
Brittle solids—not malleable or ductile
Little or no metallic luster
Gain electrons easily
Dull, not metallic-shiny, although they may be colorful
Lower melting points and boiling point than the metals

Comparing the Metals and Nonmetals

The chart below displays a comparison of the physical and chemical properties of the metals and nonmetals. These properties apply to the metals in general (alkali metals, alkaline earth, transition metals, basic metals, lanthanides, actinides) and nonmetals in general (nonmetals, halogens, noble gases).

	Metals	Nonmetals
chemical properties	easily lose valence electrons	easily share or gain valence electrons
	1-3 electrons (usually) in the outer shell	4-8 electrons in the outer shell (7 for halogens and 8 for noble gases)
	form basic oxides	form acidic oxides
	good reducing agents	good oxidizing agents
	have low electronegativity	have higher electronegativity
physical properties	solid at room temperature (except mercury)	may be liquid, solid, or gas (noble gases are gases)
	have metallic luster	do not have metallic luster
	good conductor of heat and electricity	poor conductor of heat and electricity
	typically malleable and ductile	usually brittle
	opaque in a thin sheet	transparent in a thin sheet