Metalloids: As we know, the elements in the periodic table are arranged as \({\rm{s,p,d}}\) and \({\rm{f}}\) blocks depending upon the orbital on which the valence or the last electron enters. However, other than the electrons, the elements present in these blocks have unique characteristics and properties. Elements in the periodic table can be classified into three types: metals, non-metals, and metalloids. While metals and non-metals have distinct differentiation between the two and have specific characteristics that differentiate them from each other, the metalloids are unique.

Since metalloids have characters of both metals and non-metals and are limited in numbers, they find use in several ways and are explored further. This article will look into metalloids and their unique properties.

What are Metalloids?

While we know all about the properties of metals and non-metals and their characteristic features, there are certain elements that possess the characteristics of both metals and non-metals. These are called Metalloids or Semi-metals. 

Know Uses of Metals and Non-metals Here

In the periodic table, the trend is such that the metallic character increases as we go from left to right in a period. However, the change from metallic to non-metallic is not quite sudden. The elements lying between these show the characters of both metals and non-metals and are called metalloids.

So, metalloids or semi-metals can be defined as those elements which show or possess the characters of both metals and non-metals and are unique in their own properties. A zig-zag line separates the metals from non-metals, and so, metalloids are also known as ‘borderline elements’.

Metalloids

Metalloids or semi-metals exists only in the \({\rm{p}}\)-block of the periodic table. Within each group of \({\rm{p}}\)-block, the non-metallic character precedes the metalloids, and as we go down the group, the metallic character increases. 

The elements which show metalloid characters in \({\rm{p}}\)-block are as follows:

Elements	Symbol	Atomic Number	Group
Boron	\({\rm{B}}\)	\(5\)	\(13\) or \({\rm{IIIA}}\)
Silicon	\({\rm{Si}}\)	\(14\)	\({\rm{1}}{{\rm{4}}^{{\rm{th}}}}\) or \({\rm{IV A}}\)
Germanium	\({\rm{Ge}}\)	\(32\)	\({\rm{1}}{{\rm{4}}^{{\rm{th}}}}\) or \({\rm{IV}}\,{\rm{A}}\)
Arsenic	\({\rm{As}}\)	\(33\)	\({\rm{1}}{{\rm{5}}^{{\rm{th}}}}\) or \({\rm{V}}\,{\rm{A}}\)
Antimony	\({\rm{sb}}\)	\(51\)	\({\rm{1}}{{\rm{5}}^{{\rm{th}}}}\) or \({\rm{V}}\,{\rm{A}}\)
Tellurium	\({\rm{Te}}\)	\(52\)	\({\rm{1}}{{\rm{6}}^{{\rm{th}}}}\) or \({\rm{VI}}\,{\rm{A}}\)
Astatine	\({\rm{At}}\)	\(85\)	\({\rm{1}}{{\rm{7}}^{{\rm{th}}}}\) or \({\rm{VII}}\,{\rm{A}}\)
Polonium	\({\rm{Po}}\)	\(84\)	\({\rm{1}}{{\rm{6}}^{{\rm{th}}}}\) or \({\rm{VI}}\,{\rm{A}}\)

Typical Characteristics of Metalloids

While there are no explicit characteristics by which the metalloids can be differentiated, there are some properties of metalloids that are similar to metals and non-metals.

Metalloids are similar to metals in the fact that:

Solids at room temperature (under ordinary conditions).
b. Looks similar to metals in general appearance.
c. They can form alloys like metals when they are combined with other metals.

They possess the character of non-metals in the fact that:

a. Their conductivity is much lesser than metals.
b. They are brittle, unlike the metals, and similar to non-metals.
c. Their chemical properties are very similar to non-metals.

Metalloids as Semi-conductors and Other Uses

Semi-conductors are materials with a conductivity that is less than the metals but more than the non-metals. Metalloids form the perfect example of materials that can be used as semiconductors because they are neither too conductive as metals nor are they completely non-conductive, like non-metals. The partial conductivity displayed by the metalloids is perfectly suitable in the manufacture of semi-conductors. 

Metalloids are very useful for:

• Making alloys with other metals, such as Tin, aluminium, lead, etc.
• As Catalysts – Boron trifluoride and trichlorides act as catalysts in several organic synthesis reactions. 
• For making glasses and optoelectronics – Oxides of boron, germanium, silicon, arsenic, and antimony are used in glass manufacturing. They are used as phase-change materials in optoelectronics.
• As flame retardants – most metalloids, such as silicon, boron, arsenic, and antimony compounds are used as flame retardants.
• In pyrotechnics – Boron and silicon are used as metal fuels.

Silicon, for instance, is used in making computer chips, and several other electronic components. Several of its alloys are used in building parts of engines. Other metalloids also form alloys with metals and are extremely useful for many purposes. Metalloids are also biological agents. Boron, for example, is used in the manufacturing of boric acid, an antiseptic and anti-fungal agent.

Summary

The periodic table consists of three types of elements- metals, non-metal, and metalloids. The metalloids or semi-metals have characters that are in-between both metals and non-metals. They display the properties of both metals and non-metals, and therefore, form a bridge between these types of elements. Hence, they are also known as borderline elements. They are neither conductive nor non-conductive, and therefore, are used in semi-conductors. Metalloids belong to the p-block of the periodic table and have elements from group \(13\) to group \(–17.\) Metalloids are very useful in the making of semi-conductors, and in alloys, as catalysts and in the manufacture of glasses and in pyrotechnics.

FAQs

Q1. Which is an example of a metalloid?
Ans. An example of a metalloid is Silicon. Other examples include Boron, Germanium, and Arsenic.

Q2. What are metalloids?
Ans. Metalloids or semi-metals are elements that have the properties of both metals and non-metals or have properties that are somewhere in-between metals and non-metals. For example, they have a lustre and look like metals but do not show conductivity like metals.

Q3. What are 5 facts about metalloids?
Ans. a. Metalloids show the properties of both metals and non-metals.
b. Metalloids have the lustre and the appearance of metals.
c. All metalloids are in the p-block of the periodic table.
d. Metalloids can form alloys with metals.
e. Metalloids are also known as borderline elements since they form a border between metals and non-metals in the periodic table.

Q4. Give one commonly used recognised metalloid.
Ans. Metalloids such as Silicon and Germanium are widely used as semiconductors and are used in the manufacture of electronics and computer parts.

Q5. Give one metalloid which is less commonly recognised.
Ans. Astatine, At \((85)\) is a less commonly recognised metalloid. Polonium, Po is also less recognized and has characteristics closer to the metals.

Learn About Valence Electrons Here

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