Theory:

The elements in the periodic table are classified as metals and non-metals based on their physical and chemical properties. There are around \(95\) metals and \(17\) non-metals in the periodic table.
Non-metals are electronegative elements where they gain electrons to form a stable configuration.
Physical properties of Non-metals:
A physical property can be observed and measured without altering the sample's chemical identity. A physical property can cause a physical change but not a chemical change.
 
Let us see some of the physical properties of Non-metals:
  • State
  • Lustre
  • Malleability
  • Ductility
  • Hardness
  • Valency
  • Conduction
  • Density
  • Sonorous
  • Melting point and boiling point
State:
  
Most of the non-metals exist in all three states of matter at room temperature. For example, carbon (solid), bromine (liquid) and chlorine (gas).
  
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Chlorine gas
 
Lustre:
  
Non-metals are non-lustrous (as they have no metallic lustre and do not reflect light) in nature, except iodine and diamond.
 
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Diamond
 
Malleability:
  
Non-metals are non-malleable (as they are very brittle, they cannot be drawn into sheets)in nature, except carbon.
 
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Carbon
 
Ductility:
  
Non-metals are non-ductile (as they are very brittle, they cannot be drawn into wires) in nature.
 
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Brittle nature of non-metal
 
Hardness:
 
Non-metals are soft except diamond.
 
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Sulphur
 
Valency:
  
Non-metals have \(4\) to \(7\) electrons in the outermost shell.
 
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Electronic configuration of non-metal
 
Conduction:
  
Non-metals are poor conductors of heat and electricity except graphite.
 
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Insulators
 
Density:
  
Non-metals have low density.
 
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Graphite
 
Sonorous:
  
Non-metals make a dull sound.
 
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Plastics
  
Melting and Boiling point:
  
Non-metals have low melting and boiling points except sodium and potassium, which have low melting and boiling points.
 
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Low melting point of non-metal
The materials which generally possess the above properties are called Non-metals.
Example:
Oxygen, carbon, sulfur, hydrogen, phosphorous, nitrogen, chlorine etc.