ElementsWhat are the metalloids?
The metalloids lie along a stair-step line between the metals and the nonmetals, and behave partly like each. They often look like metals but are brittle, and they carry electricity only moderately. That in-between behaviour makes silicon and germanium semiconductors, the base of all modern electronics. Books do not fully agree on which elements count as metalloids. This site follows the grouping used by PubChem.
The family in numbers
Melting points in this family run from 253.9 °C (polonium) to 2,075 °C (boron). Among its solid members, the least dense is silicon (2.33 g/cm³) and the densest is polonium (9.32 g/cm³). Known since ancient times: arsenic, antimony. The most recently discovered member is polonium (1898).
All metalloids compared
| No. | Symbol | Name | Atomic mass | State | Melts at | Boils at | Density g/cm³ | Discovered |
|---|---|---|---|---|---|---|---|---|
| 5 | B | Boron | 10.81 | Solid | 2,075 °C | 4,000 °C | 2.37 | 1808 |
| 14 | Si | Silicon | 28.085 | Solid | 1,414 °C | 3,265 °C | 2.33 | 1824 |
| 32 | Ge | Germanium | 72.63 | Solid | 938.3 °C | 2,833 °C | 5.32 | 1886 |
| 33 | As | Arsenic | 74.92159 | Solid | 816.9 °C | 613.9 °C | 5.78 | Ancient |
| 51 | Sb | Antimony | 121.760 | Solid | 630.6 °C | 1,587 °C | 6.68 | Ancient |
| 52 | Te | Tellurium | 127.6 | Solid | 449.5 °C | 987.9 °C | 6.23 | 1782 |
| 84 | Po | Polonium | 208.98243 | Solid | 253.9 °C | 961.9 °C | 9.32 | 1898 |
Other families: alkali metals, alkaline earth metals, transition metals, post-transition metals, nonmetals, halogens, noble gases, lanthanides, actinides.