6 Properties Of Metalloids | Xometry

ResourcesMaterials6 Properties of Metalloids6 Properties of MetalloidsWritten byDean McClementsUpdated byDr. Mahder Tewolde PhD 5 min readPublished August 8, 2022Updated February 12, 2026

Learn more about the key properties of these elements.

Metalloids are a class of elements that have properties of both metals and nonmetals. They fall between metals and nonmetals on the periodic table. The definition of metalloids, as well as the number of elements that fall into this group, is often debated by scientists. Boron, silicon, germanium, arsenic, tellurium, and antimony are all generally accepted as being metalloid elements, and as such, will be the focus of this article. However, while polonium, astatine, and bismuth are also sometimes classified as metalloids, they will not be discussed.

This article will describe the six most essential properties of metalloids and list some key metalloid characteristics.

1. Metalloids Are Solids

All metalloids are solid at room temperature and have relatively high melting points. The melting points of the metalloids are listed in Table 1 below:

Element	Melting Temperature (°C)
ElementBoron	Melting Temperature (°C)2079
ElementSilicon	Melting Temperature (°C)1410
ElementGermanium	Melting Temperature (°C)938.3
ElementArsenic	Melting Temperature (°C)817
ElementTellurium	Melting Temperature (°C)449.5
ElementAntimony	Melting Temperature (°C)631

Table 1. Melting Temperatures of Metalloids

2. Metalloids Have a Metallic Luster and Appear to be Metals

Metalloids have the physical appearance of metals. Their metallic/reflective surface makes it immediately obvious why the name "metalloid" fits these elements. The image below illustrates the visible surface characteristics of metalloids:

The physical appearance of different metalloids

3. Metalloids Are Brittle and Easily Broken

Metalloids cannot be formed using the cold-forming techniques generally used for metals because they are very brittle. Metalloids will tend to fail due to brittle fracture or crumbling.

4. Metalloids Have the Ability To Conduct Electricity, but Not As Well as Metals

Metalloids can be manipulated to behave as either conductors or insulators. This semiconducting behavior is what makes some, if not all, metalloids so useful in controlling complex electronic circuits. Metalloids are modified into semiconductors useful for a wide range of circumstances by a process called "doping." Doping is the process of adding impurities to alter the properties of intrinsic semiconductors, like metalloids. Despite their valuable semiconducting capabilities, metalloids are still poor conductors of electricity compared to metals.

5. Metalloids Behave More Like Nonmetals in That They Easily Form Anions, Have Multiple Oxidation States, and Form Covalent Bonds

The oxidation state of an element refers to the number of electrons an atom either gains or loses to bond chemically with another atom. In the case of metalloids, single covalent bonds are more common. A covalent bond refers to the situation where a pair of atoms shares one electron. The oxidation states of the metalloid elements are listed in Table 2 below:

Elements	Oxidation State (Positive)	Oxidation State (Negative)
ElementsBoron	Oxidation State (Positive)=+3, +2, +1	Oxidation State (Negative)-5, -1
ElementsSilicon	Oxidation State (Positive)=+4, 0	Oxidation State (Negative)-4
ElementsGermanium	Oxidation State (Positive)=+2, +4
ElementsArsenic	Oxidation State (Positive)=+3, +5	Oxidation State (Negative)-3
ElementsTellurium	Oxidation State (Positive)=+4, +6	Oxidation State (Negative)-2
ElementsAntimony	Oxidation State (Positive)=+3, +5	Oxidation State (Negative)-3

Table 2. Metalloids’ Oxidation States

6. Metalloids' Ionization Energies and Electronegativities Are Between the Values of Metals and Nonmetals

Ionization energy refers to the amount of energy that is required to strip an electron from a neutral atom to form an ion. The first ionization energy is the energy required to remove the first electron, which is the easiest to remove. Electronegativity refers to how easily an atom will attract electrons when forming a chemical bond. The higher the number, the stronger the attraction. Therefore, the higher the electronegativity value, the more likely it is that the element will attract electrons. If two elements with similar electronegativities bond, they form a pure covalent bond that shares electrons equally. However, if elements have different electronegativities, the resulting molecule will be polarized. This is because the electrons in the bond will be attracted more strongly to the element with stronger electronegativity. 

The metalloids listed in Table 3 below have ionization energies and electronegativities as shown:

Elements	1st Ionization Energy (eV)	Electronegativity (Pauling Scale)
ElementsBoron	1st Ionization Energy (eV)8.298	Electronegativity (Pauling Scale)2.04
ElementsSilicon	1st Ionization Energy (eV)8.1517	Electronegativity (Pauling Scale)1.9
ElementsGermanium	1st Ionization Energy (eV)7.9	Electronegativity (Pauling Scale)2.01
ElementsArsenic	1st Ionization Energy (eV)9.8152	Electronegativity (Pauling Scale)2.18
ElementsTellurium	1st Ionization Energy (eV)9.0096	Electronegativity (Pauling Scale)2.1
ElementsAntimony	1st Ionization Energy (eV)8.64	Electronegativity (Pauling Scale)2.05

Table 3. Metalloids’ 1st Ionization Energies and Electronegativities

Metalloids are elements that exhibit characteristics of both metals and nonmetals, bridging the gap between the two on the periodic table. The article highlights six key properties: they are solid at room temperature, have a metallic sheen, are brittle, conduct electricity moderately, form covalent bonds, and possess intermediate ionization energies and electronegativities. Their semiconducting behavior, particularly in elements like silicon and boron, makes them vital for electronic and industrial applications.Mahder Tewolde, Ph.D., PENote from the Editor

What Distinguishes Metalloids?

The key distinguishing properties of metalloids are that they have characteristics of both metals and nonmetals. Their ability to act as semiconductors is a unique and essential feature of some metalloids. This makes metalloids indispensable in an era when electronic circuits are everywhere.

For more information, see our guide on the Elements of Metalloids.

Which Property is the Most Useful for Identifying a Metalloid?

Most metalloids can be visually identified by their metallic appearance. Identifying metalloids by their chemical attributes is generally more difficult, as there are no properties of metalloids that make them stand out distinctly enough from other elements.

What Elements are Commonly Referred to as Metalloids?

The elements that are commonly referred to as metalloids are listed in Table 4, along with brief descriptions and a few typical applications:

Element	Description	Application
ElementBoron	DescriptionAn allotropic semimetal that is extremely hard and heat-resistant. Has an atomic number of 5.	ApplicationUsed with silicon to make thermal shock-resistant glass.
ElementSilicon	DescriptionA gray and shiny semiconductive metal. It has high melting (1,410 °C) and boiling points (3,265 °C). Has an atomic number of 14.	ApplicationCommonly used for semiconductors.
ElementGermanium	DescriptionIt is hard and brittle in its elemental form. Has an atomic number of 32.	ApplicationLess commonly used for semiconductors.
ElementArsenic	DescriptionA steel-gray semimetal known for being poisonous. It has an atomic number of 33.	ApplicationOften used as an insecticide.
ElementTellurium	DescriptionBrittle in its elemental form. It is a chalcogen, along with selenium and sulfur. It has an atomic number of 52.	ApplicationUsed as a steel additive to improve machinability.
ElementAntimony	DescriptionA hard and brittle semimetal with an atomic number of 51.	ApplicationUsed to color paints; often alloyed with lead.

Table 4. Metalloids: Descriptions and Typical Applications

Differences Between Metals and Nonmetals

Some differences between metals and nonmetals are shown in Table 5 below:

Properties	Metals	Nonmetals
PropertiesElectrical Conductivity	MetalsGenerally conductive	NonmetalsNonconductive; behave as insulators
PropertiesMechanical Properties	MetalsIt can be hard or soft, ductile or brittle	NonmetalsGenerally brittle and hard, not suitable for mechanical applications
PropertiesThermal Conductivity	MetalsMetals are more thermally conductive than nonmetals	NonmetalsNonmetals are not very thermally conductive
PropertiesForm	MetalsMost metals are solids at room temperature (barring a few exceptions like gallium or mercury)	NonmetalsNonmetals can be in the form of gases (e.g., hydrogen), liquids (e.g., bromine), or solids (e.g., carbon)

Table 5. Comparison of Metals and Nonmetals 

Common FAQs About Metalloid Properties

What is the Composition of Metalloids?

Metalloids are fundamental elements, just like all the other elements on the periodic table. Like all elements, they are composed of protons, neutrons, and electrons.

What is a Metalloid's Most Useful Property?

Metalloids’ most useful property is their semiconducting behavior. They are widely used in electronics. The conductivity of semiconducting metalloids can be enhanced using a technique called doping. Doping consists of the addition of small amounts of impurities to the base semiconductor to change its charge-carrying properties in desirable ways. Additionally, metalloids are often used as alloying elements.

Are Metalloids Brittle or Malleable?

Yes, metalloids are brittle. This means that when deformed, they tend to crack instead of deforming elastically or plastically. Therefore, they cannot be used for structural applications. Metalloids are often used as alloying elements in metals or as semiconductors in electrical devices.

How Do You Categorize a Metalloid?

Metalloids are categorized neither as metals nor as nonmetals. This is because they have properties intermediate between those of metals and non-metals. They exist in the space between elements that are definitely metals and those that are definitely nonmetals, due to their unique combination of characteristics from both of these other groups.

How Can the Electronic Configuration of a Metalloid be Determined?

The electron configuration is determined by the number of electrons in an element. Electrons will fill the orbitals predictably and always occupy the lowest-energy orbital available. Electron configuration refers to the way in which electrons are arranged around the nucleus of an atom.

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Dean McClementsDean McClements is a B.Eng Honors graduate in Mechanical Engineering with over two decades of experience in the manufacturing industry. His professional journey includes significant roles at leading companies such as Caterpillar, Autodesk, Collins Aerospace, and Hyster-Yale, where he developed a deep understanding of engineering processes and innovations.

Read more articles by Dean McClements

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