Non-metals and their general properties
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Non-metals and their general properties
Metal and Non-metals of Class 8
NON-METALS AND THEIR GENERAL PROPERTIES
Non-metals are present on the right hand side of the periodic table (except Hydrogen).
PHYSICAL PROPERTIES OF NON-METALS:
The important physical properties of non-metals are listed below:
- Non-metals are brittle.
- Non-metals are not ductile.
- Non-metals are bad conductor of heat and electricity.
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Graphite is a good conductor because of the presence of a free electron. It is used as positive electrode in dry cells. |
- Non-metals are not lustrous and-cannot be polished.
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Graphite and Iodine are lustrous non-metals. |
- Non-metals may be solid, liquid, or gases at room temperature. Solid: Carbon, sulphur and iodine.
Gases : Oxygen, hydrogen, nitrogen etc.
Bromine is the only non-metal which exists as a liquid at room temperature.
Liquid non-metal : Bromine
Diamond (in allotropic form of non-metal Carbon) is the HARDEST NATURAL substance known . |
Diamond is lustrous and hard non-metal |
Non-metals have generally low melting and boiling points.
Exception: Graphite, another allotropic form of Carbon, has a melting point of about 3730°C. Other exceptions are C, B, Si which have high melting and boiling points.
Non-metals have low densities.
Exception: Iodine has high density and diamond which is almost as heavy as AI.
Malleability : Non-metals are not malleable i.e. sheets cannot be made from non-metals.
Tensile strength : Non-metals do not have the property of tensile strength.
Exception: Carbon fibre is as tensile as steel.
Sonorous : Non-metals are non-sonorous, i.e., when struck with a hammer they do not produce sound.
Colour : Chlorine is a greenish yellow gas, while bromine is brown in colour. Iodine is violet in colour, while oxygen and nitrogen are colourless gases.
DIFFERENCES IN PHYSICAL PROPERTIES OF METALS AND NON-METALS:
| PROPERTY | METALS | NON-METALS |
| State: |
Solids at room temperature.
Exceptions: Hg and Ga are liquids |
Mostly gases
Exception: Some of the solid non-metals are C, S, P, I2 and bromine is a liquid non-metal. |
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Melting point
and boiling point: |
Very high melting point and boiling point.
Exceptions: Na, K, Hg have low melting points and boiling points. Ga has low melting point but high boiling point. |
Low melting points and boiling points.
Exceptions: C, Si and B have high melting points and boiling points. |
| Hardness: |
Generally hard.
Exceptions: Na and K are soft. |
Solid non-metals are brittle. Exception: Diamond is the
hardest naturally occurring substance. |
| Density: |
Have high density.
Exception: Li, Na and K have density lower than water (1gm/cm3) |
Have low density.
Exception: Diamond |
| Conductivity: |
Good conductors of heat and electricity.
Exceptions: Bi and W are poor conductors of electricity. |
Bad Conductors of heat and electricity.
Exception: Graphite and gas carbon are good conductors of electricity. |
| Luster: | Have luster |
No luster.
Exceptions: I2 and graphite |
| Tensile strength; |
High tensile strength
Exception: Zn has very less tensile strength. |
Do not have tensile strength. Exception: Carbon fibre,
a recently developed allotrope of carbon. |
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Malleability and
ductility: |
Generally malleable and ductile. Exception: Zinc is not malleable
and ductile |
Non-malleable and non-ductile. Exception: Carbon
fibres are ductile |
| Sonority | Sonorous | Non-sonorous |
