Nonmetal

A periodic table extract highlighting nonmetals

alt=A grid with 7 rows labeled periods "1" to "7" and 10 columns labeled as groups "1", "2", "3–11", and "12" to "18".
¶ Most cells represent one chemical element and are labeled with its 1 or 2 letter symbol in a large font above its name. Cells in column 3 (labeled "3–11") represent a series of elements and are labeled with the first and last element's symbol.
¶ Row 1 has cells in the first and last columns, with an empty gap between. Rows 2–3 have 8 cells, with a gap between the first 2 and last 6 columns. Rows 4–7 have cells in all 10 columns.
¶ A bold falling staircase line separates the rightmost 6/5/4/3/2/1 cells in rows 2–7.
¶ 17 cells above and right of the staircase are tan-colored: both cells row 1 and all cells to its right except the first one.
¶ 9 cells along the staircase are specially colored: gray in rows 2–5 and brown in rows 6-7: the first cell after it in rows 2–7 and first cell before in rows 4/5/7.
¶ The rest of the cells have light gray letters on a white background.

17 always/usually considered nonmetals

6 metalloids, sometimes considered nonmetals

3 status as nonmetal or metal unconfirmed

In the context of the periodic table, a nonmetal is a chemical element that mostly lacks distinctive metallic properties. Physically, nonmetals range from colorless gases such as hydrogen to lustrous crystalline solids such as iodine. They are usually less dense than metals and are often poor conductors of heat and electricity. Chemically, they have moderate to very high electronegativity—a tendency to attract electrons in a chemical bond—and their oxides tend to be acidic.

Seventeen elements are widely recognized as nonmetals. Additionally, some or all of six borderline elements (metalloids) are sometimes counted as nonmetals.

The two lightest nonmetals, hydrogen and helium, together make up about 98% of the mass of ordinary matter in the observable universe. Five nonmetallic elements—hydrogen, carbon, nitrogen, oxygen, and silicon—make up the bulk of Earth’s atmosphere, oceans, biosphere, and crust. Metals, however, are thought to constitute slightly more than half of Earth’s total mass.

Chemical compounds and alloys involving multiple elements including nonmetals are widespread. Industrial uses of nonmetals as the dominant component include in electronics, combustion, lubrication and machining.

Most nonmetallic elements were identified in the 18th and 19th centuries. While a distinction between metals and other minerals had existed since antiquity, a classification of chemical elements as metallic or nonmetallic emerged only in the late 18th century. Since then about twenty properties have been suggested as criteria for distinguishing nonmetals from metals. In contemporary research usage it is common to use a distinction between metal and not-a-metal based upon the electronic structure of the solids; the elements carbon, arsenic and antimony are then semimetals, a subclass of metals. The rest of the nonmetallic elements are insulators, some of which such as silicon and germanium can readily accommodate dopants that change their electrical conductivity leading to semiconducting behavior.