A nonmetal is a chemical element with several properties that are opposite those of a metal. Based on their properties, the elements of the periodic table are generally classified as metals, nonmetals, and metalloids.
Only 18 elements of the periodic table are generally considered nonmetals, whereas more than 80 elements are considered metals. However, nonmetals and their compounds make up most of the crust, atmosphere, and oceans of the Earth, as well as constituting most of the bulk tissues of living organisms.
List of nonmetals
The elements generally regarded as nonmetals are noted below, along with their groups in the periodic table.
- Group 1: Hydrogen (H)
- Group 14: Carbon (C)
- Group 15 (the pnictogens): Nitrogen (N), phosphorus (P)
- Group 16 (the chalcogens): Oxygen (O), sulfur (S), selenium (Se)
- Group 17 (the halogens), all elements: Fluorine (F), chlorine (Cl), bromine (Br), iodine (I), astatine (At)
- Group 18 (the noble gases), all elements: Helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), radon (Rn)
If one looks at their positions in the periodic table, it is clear that almost all the nonmetals (except for hydrogen) are located on the upper right-hand side of the table. They are separated from metals by the group of elements known as metalloids.
Occurrence in nature
Hydrogen, carbon, nitrogen, oxygen, sulfur, and the noble gases can be found in the form of free (uncombined) elements as well as compounds in nature. The other nonmetals occur mainly as compounds. Examples of compounds of nonmetals include the carbonates, nitrates, oxides, sulfides, sulfates, phosphates, and halides.
The Earth's crust, atmosphere, and oceans are constituted mostly of nonmetals and their compounds. Moreover, the bulk tissues of living organisms are composed mainly of nonmetals and their compounds.
There is no rigorous definition for the term "nonmetal"—it covers a general spectrum of behavior. The following are some general properties considered characteristic of nonmetals.
- Nonmetals are usually poor conductors of heat and electricity, whereas metals are relatively good conductors. An exception is graphite, an allotrope of carbon, which is a good conductor of electricity.
- Nonmetals form acidic oxides. By contrast, metals generally form basic oxides.
- In the solid form, nonmetals are dull and brittle. Metals, on the other hand, are generally lustrous, ductile, and malleable.
- Nonmetals usually have lower densities than metals.
- The melting points and boiling points of nonmetals are significantly lower than those of metals.
- Nonmetals have high electronegativity values.
- Most nonmetals tend to gain electrons relatively easily, pulling them away from metals. Thus, nonmetals tend to form anions (negatively charged ions), whereas metals tend to form cations (positively charged ions). The noble gases, however, are relatively unreactive and are exceptions.
- Most nonmetals have high values of ionization energy.
- In forming molecules, nonmetals tend to share electrons to form covalent bonds.
- In terms of their electronic configuration, the outermost electron shells of most nonmetals are incomplete. These elements therefore attempt to gain electrons. The exceptions are the noble gases, which are unreactive because their outermost electron shells are complete.
At room temperature, many nonmetals (hydrogen, nitrogen, oxygen, fluorine, chlorine, and the noble gases) are gases; one nonmetal (bromine) is a liquid; the remaining nonmetals are solids. Nonmetals in the gaseous state exist as single atoms or diatomic molecules. By comparison, nearly all metals are solids at room temperature, except for mercury, which is a liquid.
Metallization at extremely high pressures
At extremely high pressures, the nonmetals tend to become metallic in nature.
- ↑ Raymond Chang, Chemistry, 9th edition (New York: McGraw-Hill Science/Engineering/Math, 2001, ISBN 0073221031).
- Brown Jr., Theodore L., H. Eugene LeMay, Bruce Edward Bursten, and Julia R. Burdge. 2002. Chemistry: The Central Science, 9th edition. Upper Saddle River, NJ: Prentice Hall. ISBN 0130669970.
- Chang, Raymond. 2006. Chemistry, 9th edition. New York: McGraw-Hill Science/Engineering/Math. ISBN 0073221031.
- Cotton, F. Albert, and Geoffrey Wilkinson. 1980. Advanced Inorganic Chemistry, 4th edition. New York: Wiley. ISBN 0-471-02775-8.
- Greenwood, N.N., and A. Earnshaw. 1997. Chemistry of the Elements, 2nd edition. Oxford: Butterworth-Heinemann, Elsevier Science. ISBN 0750633654.
- Periodic Table: Non-Metals. ChemicalElements.com. Retrieved July 24, 2008.
- Nonmetals. About.com:Chemistry. Retrieved July 24, 2008.
- Non-metal. Encyclopaedia. Retrieved July 24, 2008.
- Non-metal. Encyclopaedia. Retrieved July 24, 2008.
|Standard table | Vertical table | Table with names | Names and atomic masses (large) | Names and atomic masses (small) | Names and atomic masses (text only) | Inline F-block | Elements to 218 | Electron configurations | Metals and non metals | Table by blocks | List of elements by name|
|Groups: 1 - 2 - 3 - 4 - 5 - 6 - 7 - 8 - 9 - 10 - 11 - 12 - 13 - 14 - 15 - 16 - 17 - 18|
|Periods: 1 - 2 - 3 - 4 - 5 - 6 - 7 - 8|
|Series: Alkalis - Alkaline earths - Lanthanides - Actinides - Transition metals - Poor metals - Metalloids - Nonmetals - Halogens - Noble gases|
|Blocks: s-block - p-block - d-block - f-block - g-block|
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