Why is Boron a Metalloid? (+ 3 Things You Should Know)

Boron is classified as a metalloid because it exhibits properties of both metals and nonmetals. It has some metallic properties, such as high melting and boiling points, but also some nonmetallic properties, such as low density and poor electrical conductivity. ¹

Well, this was just a simple answer. But there are few more things to know about this topic which will make your concept super clear.

So let’s dive right into it.

Explanation: Why is boron a metalloid?

Boron is considered a metalloid because it has properties of both metals and nonmetals. 

It is a solid at room temperature, has a high melting point, and is a good conductor of heat. ²

However, it is also brittle and does not conduct electricity (at room temperature) like metals. ³

Boron also forms covalent bonds with other elements, which is a characteristic of nonmetals. ⁴

Here is a table of some of the properties of boron, metals, and nonmetals:

Property	Boron	Metal	Nonmetal
Melting point	2,076 °C 5	Varies widely	Low
Conductivity of heat	Good	Good	Poor
Conductivity of electricity	Poor	Good	Poor
Brittleness	Yes	No	Yes
Covalent bonding	Yes	No	Yes

As you can see, boron has some properties that are similar to metals and some properties that are similar to nonmetals. This is why it is classified as a metalloid.

How does boron differ from other metalloids?

Boron differs from other metalloids in a few ways:

• Atomic structure: Boron has a smaller atomic radius and lower electron affinity compared to other metalloids like silicon and germanium. This means it is less likely to bond with other elements. ⁶
• Physical properties: Boron has a much higher melting and boiling point than other metalloids. ⁷ This is because its covalent bonds are stronger and more directional, making it harder to break them apart.
• Chemical properties: Boron has a unique ability to form complex molecular structures and compounds due to its small size and electron-deficient nature. ⁸ This makes it useful in a variety of applications, such as in borosilicate glass and boron-based compounds used in drugs and pesticides. ^{9 10 11 12}

Overall, while boron shares some properties with other metalloids, its unique atomic and physical characteristics set it apart and make it a valuable material for various industrial and scientific applications.

Uses of boron based on its metalloid properties

Here are some uses of boron based on its metalloid properties:

• Borosilicate glass: Boron’s ability to form strong covalent bonds makes it an important component in borosilicate glass. This type of glass is highly resistant to thermal shock and is used in laboratory equipment, cookware, and other applications where high temperatures are involved. ¹³
• Nuclear reactors: Boron is used as a control rod material in nuclear reactors due to its ability to absorb neutrons. It is often combined with other materials, such as graphite, to create control rods that can be easily inserted or removed from the reactor core. ¹⁴
• Flame retardants: Boron compounds are used as flame retardants in a variety of materials, including textiles, plastics, and wood. Boron-based flame retardants work by releasing water and carbon dioxide when exposed to high temperatures, which can help to extinguish fires. ¹⁵
• Pesticides: Boron compounds are used in a variety of pesticides to control pests and plant diseases. Boron’s ability to form complex molecular structures makes it an effective agent for preventing the growth and reproduction of certain pests and pathogens. ^{16 17}

Overall, boron’s metalloid properties make it a versatile material with a wide range of industrial and scientific applications.

Further reading

Is Boron a Metal?
Is Boron a Nonmetal?
Why is Oxygen a Nonmetal?
Is Neon a Metal?
Is Sodium a Metal or Nonmetal? 

1. Boron – Wikipedia. (2011, December 4). Boron – Wikipedia. https://en.wikipedia.org/wiki/Boron
2. Boron – Element information, properties and uses | Periodic Table. (n.d.). Boron – Element Information, Properties and Uses | Periodic Table. https://www.rsc.org/periodic-table/element/5/boron
3. Science Innovation Centre | 005 Boron | Penrhos College. (n.d.). Penrhos College. https://penrhos.wa.edu.au/boron/
4. Covalent Bonding. (2013, October 3). Chemistry LibreTexts. https://chem.libretexts.org/Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Supplemental_Modules_(Physical_and_Theoretical_Chemistry)/Chemical_Bonding/Fundamentals_of_Chemical_Bonding/Covalent_Bonding
5. Zhang, Y., Evans, J. R. G., & Yang, S. (2011, January 11). Corrected Values for Boiling Points and Enthalpies of Vaporization of Elements in Handbooks. Journal of Chemical & Engineering Data, 56(2), 328–337. https://doi.org/10.1021/je1011086
6. ACS https://www.acs.org/content/dam/acsorg/education/students/highschool/chemistryclubs/infographics/mastering-periodic-trends-infographic.pdf
7. Boron | Properties, Uses, & Facts. (n.d.). Encyclopedia Britannica. https://www.britannica.com/science/boron-chemical-element
8. Hedberg, K. (1952, July). On the Bonding in Electron Deficient Compounds of Boron1,2. Journal of the American Chemical Society, 74(14), 3486–3489. https://doi.org/10.1021/ja01134a010
9. Smedskjaer, M. M., Mauro, J. C., Youngman, R. E., Hogue, C. L., Potuzak, M., & Yue, Y. (2011, October 18). Topological Principles of Borosilicate Glass Chemistry. The Journal of Physical Chemistry B, 115(44), 12930–12946. https://doi.org/10.1021/jp208796b
10. Das, B. C., Thapa, P., Karki, R., Schinke, C., Das, S., Kambhampati, S., Banerjee, S. K., Veldhuizen, P. V., Verma, A., Weiss, L. M., & Evans, T. (n.d.). Boron chemicals in diagnosis and therapeutics. PubMed Central (PMC). https://doi.org/10.4155/fmc.13.38
11. Song, S., Gao, P., Sun, L., Kang, D., Kongsted, J., Poongavanam, V., Zhan, P., & Liu, X. (2021, October). Recent developments in the medicinal chemistry of single boron atom-containing compounds. Acta Pharmaceutica Sinica B, 11(10), 3035–3059. https://doi.org/10.1016/j.apsb.2021.01.010
12. Boron | Public Health Statement | ATSDR. (2011, October 25). Boron | Public Health Statement | ATSDR. https://wwwn.cdc.gov/TSP/PHS/PHS.aspx?phsid=451&toxid=80
13. Group on the Evaluation of Carcinogenic Risks to Humans, I. W. (1993, January 1). Exposures in the Glass Manufacturing Industry – Beryllium, Cadmium, Mercury, and Exposures in the Glass Manufacturing Industry – NCBI Bookshelf. Exposures in the Glass Manufacturing Industry – Beryllium, Cadmium, Mercury, and Exposures in the Glass Manufacturing Industry – NCBI Bookshelf. https://www.ncbi.nlm.nih.gov/books/NBK499748/
14. Control rod – Energy Education. (n.d.). Control Rod – Energy Education. https://energyeducation.ca/encyclopedia/Control_rod
15. Dogan, M., Dogan, S. D., Savas, L. A., Ozcelik, G., & Tayfun, U. (2021, October). Flame retardant effect of boron compounds in polymeric materials. Composites Part B: Engineering, 222, 109088. https://doi.org/10.1016/j.compositesb.2021.109088
16. EPA.gov https://www3.epa.gov/pesticides/chem_search/reg_actions/reregistration/fs_PC-011001_1-Sep-93.pdf
17. Canada.ca https://www.canada.ca/content/dam/hc-sc/migration/hc-sc/cps-spc/alt_formats/pdf/pubs/pest/_decisions/rvd2016-01/rvd2016-01-eng.pdf