Copper-germanium alloy pellets, likely ~84% Cu; 16% Ge. When combined with silver the result is a tarnish resistant sterling silver. Also shown are two silver pellets.
Arsenic trioxide or white arsenic, one of the most toxic and prevalent forms of arsenic. The antileukaemic properties of white arsenic were first reported in 1878.
Optical fibers, usually made of pure silicon dioxide glass, with additives such as boron trioxide or germanium dioxide for increased sensitivity
Archaic blue light signal, fuelled by a mixture of sodium nitrate, sulfur, and (red) arsenic trisulfide
Semiconductor-based electronic components. From left to right: a transistor, an integrated circuit, and an LED. The elements commonly recognised as metalloids find widespread use in such devices, as elemental or compound semiconductor constituents (Si, Ge or GaAs, for example) or as doping agents (B, Sb, Te, for example).
Boron, shown here in the form of its β-rhombohedral phase (its most thermodynamically stable allotrope)
Silicon has a blue-grey metallic lustre.
Germanium is sometimes described as a metal
Arsenic, sealed in a container to prevent tarnishing
Antimony, showing its brilliant lustre
Tellurium, described by Dmitri Mendeleev as forming a transition between metals and nonmetals
Carbon (as graphite). Delocalized valence electrons within the layers of graphite give it a metallic appearance.
High purity aluminium is much softer than its familiar alloys. People who handle it for the first time often ask if it is the real thing.
Grey selenium, being a photoconductor, conducts electricity around 1,000 times better when light falls on it, a property used since the mid-1870s in various light-sensing applications
Iodine crystals, showing a metallic lustre. Iodine is a semiconductor in the direction of its planes, with a band gap of ~1.3 eV. It has an electrical conductivity of 1.7 × 10−8 S•cm−1 at room temperature. This is higher than selenium but lower than boron, the least electrically conducting of the recognised metalloids.
White tin (left) and grey tin (right). Both forms have a metallic appearance.

Type of chemical element which has a preponderance of properties in between, or that are a mixture of, those of metals and nonmetals.

- Metalloid

97 related topics



Electrical conductivity value falling between that of a conductor, such as metallic copper, and an insulator, such as glass.

An ingot of monocrystalline silicon
Silicon crystals are the most common semiconducting materials used in microelectronics and photovoltaics.
Karl Ferdinand Braun developed the crystal detector, the first semiconductor device, in 1874.
John Bardeen, William Shockley and Walter Brattain developed the bipolar point-contact transistor in 1947.
Mohamed Atalla developed the surface passivation process in 1957 and the MOS transistor in 1959.

Some examples of semiconductors are silicon, germanium, gallium arsenide, and elements near the so-called "metalloid staircase" on the periodic table.


Chemical element with the symbol B and atomic number 5.

Boron chunks
Ball-and-stick model of tetraborate anion, [B4O5(OH)4]2−, as it occurs in crystalline borax, Na2[B4O5(OH)4]·8H2O. Boron atoms are pink, with bridging oxygens in red, and four hydroxyl hydrogens in white. Note two borons are trigonally bonded sp2 with no formal charge, while the other two borons are tetrahedrally bonded sp3, each carrying a formal charge of −1. The oxidation state of all borons is III. This mixture of boron coordination numbers and formal charges is characteristic of natural boron minerals.
Boron (III) trifluoride structure, showing "empty" boron p orbital in pi-type coordinate covalent bonds
Ball-and-stick models showing the structures of the boron skeletons of borane clusters. The structures can be rationalised by polyhedral skeletal electron pair theory.
Ball-and-stick model of superconductor magnesium diboride. Boron atoms lie in hexagonal aromatic graphite-like layers, with a charge of −1 on each boron atom. Magnesium(II) ions lie between layers
Neutron cross section of boron (top curve is for 10B and bottom curve for 11B)
A fragment of ulexite
Borax crystals
Borosilicate glassware. Displayed are two beakers and a test tube.
Unit cell of B4C. The green sphere and icosahedra consist of boron atoms, and black spheres are carbon atoms.
Boron toxicity in rose leaves.

In its crystalline form it is a brittle, dark, lustrous metalloid; in its amorphous form it is a brown powder.


[[File:Nonmetals in the periodic table.png|thumb|upright=0.85|

Periodic table highlighting the first row of each block. Helium (He), as a noble gas, is normally shown over neon (Ne) with the rest of the noble gases. The elements within scope of this article are inside the thick black borders. The status of oganesson (Og, element 118) is not yet known.
Electronegativity values of the group 16 chalcogen elements showing a W-shaped alternation or secondary periodicity going down the group
Modern periodic table extract showing nonmetal subclasses.
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† moderately strong oxidising agent
‡ strong oxidising agent
A small (about 2 cm long) piece of rapidly melting argon ice
A cluster of purple fluorite, a fluorine mineral, between two quartzes
Selenium conducts electricity around 1,000 times better when light falls on it, a property used since the mid-1870s in light-sensing applications.
A crystal of realgar, also known as "ruby sulphur" or "ruby of arsenic", an arsenic sulfide mineral As4S4
Brownish crystals of buckminsterfullerene С60, a semiconducting allotrope of carbon
Germanium occurs in some zinc-copper-lead ore bodies, in quantities sufficient to justify extraction. The pure form costs $360 per 100 grams, as at February 2022.
The Alchemist Discovering Phosphorus (1771) by Joseph Wright. The alchemist is Hennig Brand; the glow emanates from the combustion of phosphorus inside the flask.

Density x EN plot elements.png values of the first 99 elements. Nonmetallic elements occupy the top left corner, having relatively low densities and moderate to high electronegativity values. Metalloids behave chemically like nonmetals but are sometimes treated as an intermediate class between the metals and the nonmetals.


Chemical element with the symbol Ge and atomic number 32.

Prediction of germanium, "?=70" (periodic table 1869)
Germane is similar to methane.
Nucleophilic addition with an organogermanium compound.
A typical single-mode optical fiber. Germanium oxide is a dopant of the core silica (Item 1).
A PET bottle

It is a lustrous, hard-brittle, grayish-white metalloid in the carbon group, chemically similar to its group neighbors silicon and tin.


Chemical element with the symbol Si and atomic number 14.

Jöns Jacob Berzelius discovered the silicon element in 1823.
The MOSFET, also known as the MOS transistor, is the key component of the Silicon Age. It was invented by Mohamed M. Atalla and Dawon Kahng at Bell Labs in 1959.
Silicon crystallizes in a diamond cubic crystal structure by forming sp3 hybrid orbitals.
Phase diagram of the Fe–Si system
Condensed polysilicic acid
A typical zeolite structure
Silicon carbide
A hydrosilylation reaction, in which Si–H is added to an unsaturated substrate
Structure of polydimethylsiloxane, the principal component of silicones
Ferrosilicon alloy
Silicon wafer with mirror finish
A diatom, enclosed in a silica cell wall

It is a hard, brittle crystalline solid with a blue-grey metallic luster, and is a tetravalent metalloid and semiconductor.


Chemical element with the symbol Sb and atomic number 51.

A vial containing the black allotrope of antimony
Native antimony with oxidation products
Crystal structure common to Sb, AsSb and gray As
Stibnite, China CM29287 Carnegie Museum of Natural History specimen on display in Hillman Hall of Minerals and Gems
Structure of gaseous SbF5
One of the alchemical symbols for antimony
The Italian metallurgist Vannoccio Biringuccio described a procedure to isolate antimony.
World antimony output in 2010
World production trend of antimony

A lustrous gray metalloid, it is found in nature mainly as the sulfide mineral stibnite (Sb2S3).


Chemical element with the symbol Te and atomic number 52.

Tellurium on quartz (Moctezuma, Sonora, Mexico)
Native tellurium crystal on sylvanite (Vatukoula, Viti Levu, Fiji). Picture width 2 mm.
Klaproth named the new element and credited von Reichenstein with its discovery
Tellurium production 2006
A sample of tellurium dioxide powder
A CdTe photovoltaic array

It is a brittle, mildly toxic, rare, silver-white metalloid.


Chemical element with the symbol As and atomic number 33.

Crystal structure common to Sb, AsSb and gray As
A large sample of native arsenic
Arsenic output in 2006
Alchemical symbol for arsenic
The arsenic labyrinth, part of Botallack Mine, Cornwall
Satirical cartoon by Honoré Daumier of a chemist giving a public demonstration of arsenic, 1841
Roxarsone is a controversial arsenic compound used as a feed ingredient for chickens.
An improved rice cooking approach to maximise arsenic removal while preserving nutrient elements

Arsenic is a metalloid.


Chemical element with the symbol Se and atomic number 34.

Structure of hexagonal (gray) selenium
Structure of the polymer SeO2: The (pyramidal) Se atoms are yellow.
Native selenium in sandstone, from a uranium mine near Grants, New Mexico
Selenium paradox, selenium at nutritional levels or low concentrations is required for cell homeostasis, playing a role as an anti-oxidant through selenoproteins, thus, act chemo-preventive against cancer. In contrast, supra-nutritional levels or higher concentrations act as pro-oxidant in tumour cells, thus can be exploited as chemo-therapeutic against cancer.
Relationship between survival of juvenile salmon and concentration of selenium in their tissues after 90 days (Chinook salmon ) or 45 days (Atlantic salmon ) exposure to dietary selenium. The 10% lethality level (LC10=1.84 µg/g) was derived by applying the biphasic model of Brain and Cousens to only the Chinook salmon data. The Chinook salmon data comprise two series of dietary treatments, combined here because the effects on survival are indistinguishable.

It is a nonmetal (more rarely considered a metalloid) with properties that are intermediate between the elements above and below in the periodic table, sulfur and tellurium, and also has similarities to arsenic.


Material that, when freshly prepared, polished, or fractured, shows a lustrous appearance, and conducts electricity and heat relatively well.

Iron, shown here as fragments and a 1 cm3 cube, is an example of a chemical element that is a metal.
A metal in the form of a gravy boat made from stainless steel, an alloy largely composed of iron, carbon, and chromium
Gallium crystals
A metal rod with a hot-worked eyelet. Hot-working exploits the capacity of metal to be plastically deformed.
Samples of babbitt metal, an alloy of tin, antimony, and copper, used in bearings to reduce friction
A sculpture cast in nickel silver—an alloy of copper, nickel, and zinc that looks like silver
Rhodium, a noble metal, shown here as 1 g of powder, a 1 g pressed cylinder, and a 1 g pellet
A sample of diaspore, an aluminum oxide hydroxide mineral, α-AlO(OH)
A neodymium compound alloy magnet of composition Nd2Fe14B on a nickel-iron bracket from a computer hard drive
A pile of compacted steel scraps, ready for recycling
The Artemision Bronze showing either Poseidon or Zeus, c. 460 BCE, National Archaeological Museum, Athens. The figure is more than 2 m in height.
De re metallica, 1555
Platinum crystals
A disc of highly enriched uranium that was recovered from scrap processed at the Y-12 National Security Complex, in Oak Ridge, Tennessee
Ultrapure cerium under argon, 1.5 gm
White-hot steel pours like water from a 35-ton electric furnace, at the Allegheny Ludlum Steel Corporation, in Brackenridge, Pennsylvania.
A Ho-Mg-Zn icosahedral quasicrystal formed as a pentagonal dodecahedron, the dual of the icosahedron
Body-centered cubic crystal structure, with a 2-atom unit cell, as found in e.g. chromium, iron, and tungsten
Face-centered cubic crystal structure, with a 4-atom unit cell, as found in e.g. aluminum, copper, and gold
Hexagonal close-packed crystal structure, with a 6-atom unit cell, as found in e.g. titanium, cobalt, and zinc
Niobium crystals and a 1 cm{{sup|3}} anodized niobium cube for comparison
Molybdenum crystals and a 1 cm{{sup|3}} molybdenum cube for comparison
Tantalum single crystal, some crystalline fragments, and a 1 cm{{sup|3}} tantalum cube for comparison
Tungsten rods with evaporated crystals, partially oxidized with colorful tarnish, and a 1 cm{{sup|3}} tungsten cube for comparison
Rhenium, including a 1 cm{{sup|3}} cube
Native copper
Gold crystals
Crystalline silver
A slice of meteoric iron
alt=Three, dark broccoli shaped clumps of oxidised lead with grossly distended buds, and a cube of lead which has a dull silvery appearance.| oxidised lead
A brass weight (35 g)
A droplet of solidified molten tin
alt=A silvery molasses-like liquid being poured into a circular container with a height equivalent to a smaller coin on its edge| Mercury being
Electrum, a natural alloy of silver and gold, was often used for making coins. Shown is the Roman god Apollo, and on the obverse, a Delphi tripod (circa 310–305 BCE).
A plate made of pewter, an alloy of 85–99% tin and (usually) copper. Pewter was first used around the beginning of the Bronze Age in the Near East.
A pectoral (ornamental breastplate) made of tumbaga, an alloy of gold and copper
Arsenic, sealed in a container to prevent tarnishing
Zinc fragments and a 1 cm{{sup|3}} cube
Antimony, showing its brilliant lustre
Bismuth in crystalline form, with a very thin oxidation layer, and a 1 cm{{sup|3}} bismuth cube
Potassium pearls under paraffin oil. Size of the largest pearl is 0.5 cm.
Strontium crystals
Aluminum chunk, 2.6 grams, {{nowrap|1=1 x 2 cm}}
A bar of titanium crystals
Scandium, including a 1 cm{{sup|3}} cube
Lutetium, including a 1 cm{{sup|3}} cube
Hafnium, in the form of a 1.7 kg bar

In chemistry, two elements that would otherwise qualify (in physics) as brittle metals—arsenic and antimony—are commonly instead recognised as metalloids due to their chemistry (predominantly non-metallic for arsenic, and balanced between metallicity and nonmetallicity for antimony).