Metals, nonmetals and metalloids on the periodic table

Metals

More than 80 of the 118 elements are metals, including the alkali and alkaline earth metals, the transition and post-transition metals, the lanthanides and the actinides. Metals are shiny, conduct heat and electricity well, and are malleable (they can be hammered into sheets) and ductile (they can be drawn into wires). All are solid at room temperature except mercury. In reactions they tend to lose electrons and form positive ions, and their oxides are usually basic.

Nonmetals

This view counts 18 elements as nonmetals: hydrogen, the reactive nonmetals carbon, nitrogen, oxygen, phosphorus, sulfur and selenium, the halogens and the noble gases. Solid nonmetals are usually dull and brittle, and most nonmetals conduct heat and electricity poorly; graphite, a form of carbon, is a notable exception. Eleven nonmetals are gases at room temperature and bromine is a liquid. Nonmetals tend to gain or share electrons, forming negative ions or covalent bonds, and their oxides are usually acidic.

Metalloids and the staircase line

The six metalloids shown here are boron, silicon, germanium, arsenic, antimony and tellurium. They sit along the staircase line that runs from boron down toward polonium and astatine, and their properties fall in between: they look metallic but are brittle, and they conduct electricity only moderately. That makes them useful semiconductors, the materials inside computer chips and solar cells.

Where to draw the line is partly a matter of choice. Polonium and astatine are sometimes called metalloids; this table shows polonium as a metal and astatine, with the halogens, as a nonmetal. Hydrogen sits above group 1 but is a nonmetal. The superheavy elements from meitnerium onward are marked unknown, because too few atoms have been made to test them.

The trend in metallic character

Metallic character, how readily an element loses electrons and behaves like a metal, increases down a group and decreases from left to right across a period. Group 14 shows the change clearly: carbon is a nonmetal, silicon and germanium are metalloids, and tin and lead are metals. That is why the most metallic elements are at the bottom left of the table and the most nonmetallic at the top right.

Example: silicon is shiny and gray like a metal, yet it shatters when struck, and unlike a metal it conducts electricity better as it gets warmer. Adding tiny amounts of other elements, a process called doping, controls how well it conducts, which is how transistors are made.