Ex

  Chemistry (NTSE/Olympiad)  

1. Metals & Non Metals

Important Terms And Concepts

1. Metals : Those elements which can lose electrons easily and from positive ions. They are mostly solids, possess high density. They have high melting and boiling points. They have metallic lustre and they are sonorous, i.e., produce metallic sound. They are good conductors of heat and electricity. They are usually malleable and ductile, e.g., gold , silver, copper, tin, lead, iron, mercury, cobalt, nickel, aluminium, sodium, potassium are metals.
2. Hardness : Most of the metals are hard. If you try to cut them with knife, it will not be possible in most of the metals. Some of metals like sodium, potassium are soft metals and can be cut with knife.
3. Malleability : The ability of a metals due to which it can be beaten into sheets is called malleability. Iron, copper, zinc, aluminium, magnesium are available in the form of sheets. Aluminium, steel, copper, brass, bronze are used in making utensils.
Brass and bronze are also used for making statues. Bronze is used for making medals. Aluminium and silver metals are converted in foils. Aluminium foils are used for packaing whereas silver foils are used in decorating sweets.
4. Ductility : It is the ability of metals due to which it can be drawn into wires. Copper, aluminium, iron can be drawn into wires. Silver, gold and platinum are highly ductile metals. 1 gram of gold can be drawn into 2 km long wire.
5. Effect of Tapping (Sonorous) : When metals are struck with hard substance, they produce sound, i.e., they are sonorous. Brass and bronze are highly sonorous. They are used in making bells and gongs.
6. Electrical Conductance : It is the property due to which electric current can pass through the metal. It is due to presence of free electrons or mobile electrons, e.g., copper, silver, gold, aluminium are good conductors of electricity. Silver is best conductor of electricity followed by copper, gold, aluminium and tungsten. Mercury and lead have low electrical conductivity due to high resistance.
7. Thermal Conductivity : It is the property due to which metals can conduct heat e.g., copper, silver, aluminium, gold and iron are good conductors of heat.
8. Metallic Lustre : Most of metals have shiny surface i.e., they show metallic lustre e.g., Au, Ag, Pt are lustrous.


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