Non-Metals: Definition, Physical and Chemical Properties

The elements that do not exhibit metallic characteristics are known as non-metals. They are electronegative elements, i.e. they form negatively charged ions by accepting electrons. Usually, they have 4, 5, 6, or 7 electrons in their outermost shell, making them unstable compounds. Some commonly known non-metals are Hydrogen, Carbon, Oxygen, Phosphorous, Fluorine, etc. They can exist in any form – solid, liquid, or gas. We will discuss in detail here the characteristic features of non-metals and their uses.

Read Also : Concept of Metals and Non Metals

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Non-metals in the Periodic Table

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Here’s a complete list of non-metals occurring in the periodic table along with their state at room temperature.

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General Properties

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Some properties of non-metals are-

• High ionization energy
• Highly electronegative
• Low melting point and boiling point
• Low density
• Smaller in size compared to metals
• Low electrical and thermal conductivity
• Non-malleable
• Non-ductile
• Exists in solid, liquid, or gaseous forms

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Physical Properties of Non-metals

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Apparently, we can distinguish between a metal and a non-metal by their physical properties. Non-metals can be identified as-.

• Non-lustrous: Metallic luster gives metals a shining effect, but non-metals do not possess any shine on their surface. However, non-metals like Iodine and Diamond are some exceptions.
• Non-malleable: Metals can be beaten to form thin sheets and molded into any other shape. This makes them malleable substances. Non-metals, on the contrary, are not malleable. They are brittle and tend to break when applied excessive pressure.
• Non-ductile: This is the property where the material can be easily stretched or bent to form wires. This property is absent in non-metals except Carbon. It can be made into fibers that are widely used in sports and music equipment production.
• Non-sonorous: Non-metals do not produce any sound on being struck with any other hard substance, unlike metals.
• Low melting and boiling point: Non-metals usually have a relatively low melting and boiling point. They also are low in density. Therefore, they’re poor conductors of electricity and heat. Diamond, the hardest known natural substance which is an allotrope of Carbon, is an exception to this; it has a very high melting and boiling point.
• Poor thermal and electrical conductivity: Unlike metals, non-metals are bad conductors of heat and electricity. However, there is an anomaly here as well. Graphite, which is another allotrope of Carbon is a good conductor of heat and electricity in spite of being a non-metal.

Read more : Importants notes on Metals and Non Metals

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Chemical Properties of Non-metals

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Not only physical properties, but chemical properties are also necessary to categorize elements as non-metals. For this, we’ll analyze how non-metals tend to react with different substances and compounds. Here, we must remember that non-metals are electronegative elements which means they are negatively charged ions accepting electrons.

• Reaction with Water

Non-metals do not react with water. Due to this reason, non-metals are preferably stored in water. Phosphorus, for example, is stored in water as it may catch fire when brought in contact with atmospheric oxygen. As a matter of fact, acidic oxides of non-metal dissolve in water to form acids.

• Reaction with Oxygen

All non-metals react with oxygen to form neutral or acidic oxides. For instance, Carbon reacts with Oxygen forming Carbon dioxide which is an acidic oxide.

C+ O₂ → CO₂

Similarly, Sulphur reacts with Oxygen resulting in acidic Sulphur dioxide.

S+ O₂ → SO₂

On the other hand, Hydrogen when reacting with Oxygen forms water, a neutral oxide.

2H₂+ O₂ →2H₂O

• Reaction with other non-metals

A non-metal react with another, forming covalent compounds.

Any non-metal when reacting with Chlorine forms a covalent chloride compound.

H₂+ Cl₂ →2HCl

Similarly, the reaction of Hydrogen with non-metals produces covalent hydrides.

H₂+ S → H₂S

N₂+ 3H₂ →2NH₃

• Reaction with Acids

Non-metals don’t react with acids. They cannot displace Hydrogen from the acids as they are electron-accepting elements.

• Reaction with Bases

The reaction of a non-metal with a base is very complex in nature. 

For example, when Chlorine reacts with hot and concentrated Sodium hydroxide solution, it results in the formation of Sodium hypochlorite or bleach, Sodium chloride, and water.

3Cl2+ 6NaOH →NaClO₃+ 5NaCl+3H₂O

• Reaction with Salt solutions

On the reaction of a non-metal with a salt solution, the more reactive non-metal tends to displace the less reactive one forming another salt compound separating the less reactive non-metal. For instance,

2NaBr+ Cl₂ →2NaCl + Br₂

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Uses

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Non-metals are often used in our daily routine. Some of the common uses of non-metals are-

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FAQs

Ques:  Which non-metal among the following usually exists in liquid form when at normal room temperature?(1 mark)
             a) Phosphorus      b) Iodine
             c) Bromine            d) Carbon

Ques: True/False - “Non metals are lustrous”(1 mark)

Ques:  Why, in general, non-metals don’t displace hydrogen from dilute acids? (1 mark)

Ques: Name two non-metals that are proactively used in fertilizers.(1 mark)

Ques: Which non-metal is lustrous?(1 mark)