Where Are Metalloids on The Periodic Table?

What are the metalloids?

A metalloid can be explained as a pretentious chemical element that has characteristics of both a non-metal and metal. The most essential metalloids are boron, silicon, germanium, arsenic, antimony, tellurium, and polonium.

As can be seen on the common periodic table, these elements lie diagonally across the p-block starting from boron and ending at astatine, therefore having a range of silicon.

Some periodic tables have a dividing line between metals and nonmetals, and under this line, the metalloids are listed.

Metalloids are usually brittle nonconductive material with a medium ability to conduct electricity and look like a metal.

These elements are most likely to behave as non metals, therefore the metalloids posses the ability to alloys forming metals.

Other properties and traits of the metalloid elements are often inbetween. Overall nonmetals are not extensively used for structures due to their brittle nature.

Their constituents and compounds can be found in alloys, catalysts, biological agents, glasses, flame retardants, optical storage, optoelectronics, and even in semiconductors, pyrotechnics, and electronics.

Where Are Metalloids On The Periodic Table?

Metalloids are situated in the range in between nonmetals and metals. This dividing line as observed in different forms can be found on some periodic tables.

Elements below and to the left of the line exhibit greater metallic character, while elements above and to the right exhibit greater non-metallic character.

When presented as a regular stair step, elements with the highest critical temperatures per their groups (Li, Be, Al, Ge, Sb, Po) sit directly below the line.

The orange colour on the periodic table represents metalloids, which means they are located in between nonmetals and metals.

To simplify, metalloids are located on the diagonal region of the p block of the periodic table. This also means they are on the right side of the post-transition metals and the left side of nonmetals.

Characteristic Properties of Metalloids

• Metalloids tend to look like metals, although they usually act like non-metals.
• Metalloids are brittle materials that have a glassy luster and are, at room temperature, in the solid state.
• They usually possess intermediate and quite high values of electric conductivity.
• Metalloids are believed to possess band structures of electronic states which classify these elements as semimetals or semiconductors.
• These elements possess moderate ionization energies and values of electronegativity.
• Metalloids tend to be amphoteric or form weakly acidic oxides.
• These elements are capable of forming municipal alloys.
• Essentially, metalloids possess a great variety of such intermediate traits and characteristics.

Properties of Metalloids

Metalloids generally appear metallic, but act mostly as nonmetals. They possess the physical characteristics of shiny, brittle solids that can conduct electricity to a moderate degree, and have the band structure of either a semiconductor or semimetal.

They mostly behave as (rather) nonmetals, have intermediate ionization energies, zero to weakly electronegative values, and amphoteric or weakly acid oxides.

Most of the physical and chemical characteristics are, in some other regard, of intermediate quality.

Physical Properties of Metalloids

Usually, the physical properties of metalloids fall between metals and nonmetals. Some important factors are given below: 

• Appearance. At room temperature, metalloids are brittle solids with a metallic luster. They have a shiny, metallic appearance yet are brittle enough to break. For instance, silicon is a blue-grey crystalline solid that is hard and brittle. Antimony is a silvery lustrous gray metalloid. 
• Boiling and Melting Points. Metalloids have intermediate boiling and melting points than metals and nonmetals. Silicon and germanium have melting points of 1410 °C and 938.3 °C, respectively, while boron is 2079 °C. These points are lower than the majority of metals, but higher than nonmetals. 
• Density. These values vary, but as a whole, metalloid densities fall between nonmetals and metals. The densities of antimony and tellurium are 6.697 g/cm3 and 6.24 g/cm3, while arsenic is 5.727 g/cm3.
• Electrical Conductivity. Metalloids fall short of metals when it comes to conducting electricity. In fact, some maralloids exibit semiconducting properties. This means that they are able to conduct electricity or inhibit its flow based on impurity changes or the temperature. However, metalloids are more nonmetallic elements. For instance, silicon and germanium are semiconductors which lies between nonmetals and metals.
• Allotropes. Some other metalloids have allotropy or physicially different forms with differing define properties. Most common arsenic allotropes has gray, yellow and black arsenic, most commonly used is gray.
• Thermal Conductivity. As for nonmetals, metalloids are better heat conductors but worse than metals. The thermal conductivity of metalloids depends on the specific element. Some metalloids possess low thermal conductivity whereas others possess higher than usual thermal conductivity. This property is employed in the production of thermoelectric instruments.
• Brittleness. In contrast to other ductile, daffy metals, metalloids tend to be much more brittle. Meaning, they tend to break or shatter when stressed or forced more easily than most.
• Hardness. The hardness of metalloids varies. For example, arsenic has a Mohs hardness of 3.5, while boron has a Mohs hardness of 9.3. In comparison, diamond has a Mohs hardness of 10 and gold has a Mohs hardness of 2.5.

Chemical Properties of Metalloids

Metalloids will typically behave chemically like nonmetals. Some typical chemical properties of metalloids are listed below:

• Reactivity with Nonmetals: Metalloids are chemically reactive and tend to gain or lose electrons to form negatively or positively charged ions, respectively. They readily form compounds, especially with nonmetals. For example, silicon reacts with halogens to form silicon tetrahalides, and boron forms boron trifluoride with fluorine.
• Oxidation States: Common oxidation states of metalloids include +3, +2, -4, and -2. For example, boron exhibits +3 in boron trichloride, while silicon is -4 in silicon dioxide. Arsenic and antimony commonly exhibit +3 and +5 oxidation states.
• Electronegativity: Electronegativity is the ease with which an atom attracts elements when creating a chemical bond. The higher the number, the more powerful the attraction. Metalloids generally have electronegativity values ranging from 1.8 to 2.2. This intermediate electronegativity gives metalloids the ability to form ionic and covalent bonds.
• Covalent Bonds: Metalloids make covalent bonds but do not produce monatomic ions like metals.
• Alloy Formation: Metalloids can be mixed with other metals to create alloys. Antimony is combined with lead to make antimonial lead alloys used in ammunition.
• Reactivity with Acids: Most metalloids do not react vigorously with acids. For example, silicon, germanium, and polonium do not react with most acids due to their insolubility and formation of a protective oxide layer. However, arsenic, antimony, and bismuth react with strong oxidizing acids like nitric acid. Hydrochloric acid does not oxidize them.

Examples of Metalloids on the Periodic Table

The six commonly recognised metalloids are boron, silicon, germanium, arsenic, antimony and tellurium.

Five elements are less frequently so classified: carbon, aluminium, selenium, polonium and astatine.

Commonly Recognised Metalloids

#1. Boron.

Boron is a versatile element that can be incorporated into a number of compounds. Borosilicate glass is extremely resistant to thermal shock.

Extreme changes in the temperature of objects containing borosilicate will not create any damage to the material, unlike other glass compositions, which would crack or shatter.

Because of their strength, boron filaments are used as light, high-strength materials for airplanes, golf clubs, and fishing rods.

Sodium tetraborate is widely used in fiberglass as insulation and also is employed in many detergents and cleaners.

#2. Silicon.

Silicon is a typical metalloid. It has luster like a metal but is brittle like a nonmetal. Silicon is used extensively in computer chips and other electronics because its electrical conductivity is in between that of a metal and a nonmetal.

It is a potent semiconductor, meaning it conducts electricity more efficiently at higher temperatures. Silicon compounds called silicates make up almost 90% of the earth’s crust, pure silicon is rare.

It is, however, relatively common in asteroids, moons, and cosmic dust. Silicates are frequently used in the manufacturing of cement, porcelain, and ceramics.

In the 21st century, silicon has had a massive influence on the world economy through its importance in the development of semiconductor electronics.

Pure silicon has been vital to the development of integrated circuit chips and transistors, both of which are crucial components of modern electronic devices, such as cell phones, televisions, and household appliances.

#3. Germanium.

Germanium is a shiny grey-white solid. It has a density of 5.323 g/cm3 and is hard and brittle. It is mostly unreactive at room temperature but is slowly attacked by hot concentrated sulfuric or nitric acid.

Germanium also reacts with molten caustic soda to yield sodium germanate Na2GeO3 and hydrogen gas. It melts at 938 °C.

It is also a good semiconductor and is rarely found in its pure elemental form on earth. Germanium frequently crystallizes into a diamond structure.

Germanium was predicted to exist by Dimitri Mendeleev years before it was actually discovered.

He was also able to predict many of its properties using his understanding of periodic trends and knowledge of other metalloids and nearby elements.

Like silicon, germanium is also critical to modern technology, although it is primarily used in different applications than its metalloid cousin.

Germanium is often used for infrared optics, solar energy, and numerous metal alloys.

#4. Arsenic.

Arsenic is a grey, metallic-looking solid. It has a density of 5.727 g/cm3 and is brittle, and moderately hard (more than aluminum; less than iron).

It is stable in dry air but develops a golden bronze patina in moist air, which blackens on further exposure.

Arsenic is attacked by nitric acid and concentrated sulfuric acid. It reacts with fused caustic soda to give the arsenate Na3AsO3 and hydrogen gas.

Arsenic sublimes at 615 °C. The vapor is lemon-yellow and smells like garlic. Arsenic only melts under a pressure of 38.6 atm, at 817 °C.

It readily forms covalent bonds with nonmetals. Arsenic has applications with regard to alloys, electronics, and pesticides/herbicides, but the use of arsenic for these applications is decreasing due to the toxicity of the metal.

Its effectiveness as an insecticide has led arsenic to be used as a wood preservative. It is classified as a Group-A carcinogen.

Despite its toxicity, very small quantities of arsenic are required for human metabolism, but the mechanism for this is unknown.

#5. Antimony.

Antimony is a silver-white solid with a blue tint and a brilliant luster. It has a density of 6.697 g/cm3 and is a brittle and moderately hard material that is a poor conductor of electricity.

It is stable in air and moisture at room temperature. Used with lead, antimony increases the hardness and strength of the mixture.

This material plays an important role in the fabrication of electronic and semiconductor devices.

About half of the antimony used industrially is employed in the production of batteries, bullets, alloys, cables, and plumbing equipment.

As is consistent with other metalloids, highly purified antimony can be used in semiconductor technologies.

It is found in nature at about ⅕ the abundance of Arsenic. Antimony has a similar atomic structure to arsenic as well, with three half-filled electron shells in the outermost shell.

It typically forms covalent bonds and is highly reactive with halogens, such as sulfur, and produces a brilliant blue flame when burned.

#6. Tellurium.

Tellurium is a silvery-white shiny solid. It has a density of 6.24 g/cm3, is brittle, and is the softest of the commonly recognized metalloids, being marginally harder than sulfur.

Large pieces of tellurium are stable in the air. The finely powdered form is oxidized by air in the presence of moisture.

Tellurium reacts with boiling water, or when freshly precipitated even at 50 °C, to give the dioxide and hydrogen.

Tellurium is a metalloid that exhibits a similar description to antimony. Tellurium is highly reactive with sulfur and selenium and shows a green-blue flame when burned.

Tellurium is industrially used as a steel additive and can be alloyed with aluminum, copper, lead, or tin.

Like antimony, tellurium can also strengthen other metals, but can also reduce corrosion when added to the aforementioned metals.

Additionally, tellurium serves as a strong semiconductor, particularly when exposed to light. In nature, most tellurium is found in coal, though trace amounts are found in some plants.

Examples of elements That are Irregularly Recognized as A Metalloids

#7. Polonium.

Polonium is a chemical element; it has symbol Po and atomic number 84.

A rare and highly radioactive metal (although sometimes classified as a metalloid) with no stable isotopes.

Polonium is a chalcogen and chemically similar to selenium and tellurium, though its metallic character resembles that of its horizontal neighbors in the periodic table: thallium, lead, and bismuth.

Due to the short half-life of all its isotopes, its natural occurrence is limited to tiny traces of the fleeting polonium-210 (with a half-life of 138 days) in uranium ores, as it is the penultimate daughter of natural uranium-238.

#8. Astatine.

Astatine is the 85th element of the periodic table with a symbol ‘At’.

It is a radioactive element and is said to be the most heavier among the halogens. This element exhibits similar chemical properties that of the element iodine.

The isotopes of astatine have a short life of about 8.1 hours, and some isotopes are said to be unstable. It has about seven isotopes. This element appears as a black solid with a metallic look.

It is considered as one of the rarest occurring natural element. About 2.36 × 10²⁵ grams of the earth’s crust comprises of astatine which measures about lesser than 1 gram. Astatine is mainly formed by the decay of thorium and uranium.

Examples of elements That are Less Commonly recognized as a Metalloids

#9. Selenium.

Selenium is a chemical element; it has the symbol Se and atomic number 34. It has various physical appearances, including a brick-red powder, a vitreous black solid, and a grey metallic-looking form.

It seldom occurs in this elemental state or as pure ore compounds in Earth’s crust. Selenium was discovered in 1817 by Jöns Jacob Berzelius, who noted the similarity of the new element to the previously discovered tellurium (named for the Earth).

Selenium is found in metal sulfide ores, where it substitutes for sulfur. Commercially, selenium is produced as a byproduct in the refining of these ores.

Minerals that are pure selenide or selenate compounds are rare. The chief commercial uses for selenium today are glassmaking and pigments.

Selenium is a semiconductor and is used in photocells. Applications in electronics, once important, have been mostly replaced with silicon semiconductor devices.

Selenium is still used in a few types of DC power surge protectors and one type of fluorescent quantum dot.

 Examples of elements That are Rarely recognized as a Metalloids

#10. Carbon.

Carbon is a chemical element; it has symbol C and atomic number 6. Carbon makes up about 0.025 percent of Earth’s crust.

Carbon is the 15th most abundant element in the Earth’s crust, and the fourth most abundant element in the universe by mass after hydrogen, helium, and oxygen.

Carbon’s abundance, its unique diversity of organic compounds, and its unusual ability to form polymers at the temperatures commonly encountered on Earth, enables this element to serve as a common element of all known life.

It is the second most abundant element in the human body by mass (about 18.5%) after oxygen.

#11. Aluminium.

Aluminium is the most abundant metal in the Earth’s crust (8.1%) but is rarely found uncombined in nature. It is usually found in minerals such as bauxite and cryolite.

These minerals are aluminium silicates. Most commercially produced aluminium is extracted by the Hall Héroult process.

Because of its chemical activity, aluminum never occurs in the metallic form in nature, but its compounds are present to a greater or lesser extent in almost all rocks, vegetation, and animals.

Aluminum is concentrated in the outer 16 km (10 miles) of Earth’s crust, of which it constitutes about 8 percent by weight; it is exceeded in amount only by oxygen and silicon.

The name aluminum is derived from the Latin word alumen, used to describe potash alum, or aluminum potassium sulfate, KAl(SO₄)₂∙12H₂O.

Applications of Metalloids

Typical metalloids have a metallic appearance, may be brittle and are only fair conductors of electricity.

They can form alloys with metals, and many of their other physical properties and chemical properties are intermediate between those of metallic and nonmetallic elements.

They and their compounds are used in alloys, biological agents, catalysts, flame retardants, glasses, optical storage and optoelectronics, pyrotechnics, semiconductors, and electronics.

Metalloids and the compounds of metalloids are widely used as alloys, biological agents, flame retardants, catalysts, glasses, and optical storage media.

Metalloids are also known to have applications in optoelectronics, semiconductors, pyrotechnics, and electronics.

Alloys formed when combined with transition metals are extremely well-represented when it comes to the lighter metalloids. Boron has the ability to form intermetallic compounds.

This element also has the ability to form alloys with these MnB composition metals if the value of n is greater than 2.

In fact, ferroboron (which contains 15 per cent boron) is widely used in order to inject boron into steel.

Furthermore, nickel-boron alloys are used as ingredients in the engineering industry for welding alloys and case hardening compositions.

Silicon alloys of aluminium and iron are widely used in the construction and automotive industries. Germanium is known to form several alloys, especially the coinage metals in particular.

Medical Applications of Metalloids

Each and every one of the six elements that are widely known as metalloids are known to be either toxic, or to have medicinal and nutritional properties.

For example, compounds of antimony and arsenic are known to be especially toxic. However, boron, arsenic, and silicon are extremely important trace elements.

The four elements boron, arsenic, silicon, and antimony are known to have many medical uses. The remaining two elements (germanium and tellurium) are known to have great potential for medicinal applications.

Furthermore, boron is used in herbicides and also in insecticides. This element is an active trace element, which has several antiseptic, antiviral, and antifungal properties in the form of boric acid.

FAQs