118 different elements have been discovered and can be present either in the Free State or in combined state in the earth’s crust.
These elements are known as metals and non-metals.
While metals find use in utensils, coins, jewelry, dyes and drugs, non-metals are used in small quantities but are very essential in daily life.
METALS:
Metals are the elements which form positive ions by losing electrons or by donating electrons. An exception occurs in the case of hydrogen.
Metals are known as electropositive elements because they can form positive ions by losing electrons.
Some of the examples of metals are: Iron, Aluminium, Copper, Silver, golf, Platinum, Zinc, Tin, lead, Mercury, Sodium, Potassium, Calcium and Magnesium.
A majority of the known elements are metals. Metallic elements occur in solid state except mercury which occurs in liquid state.
NON-METALS
Non-metals are the elements which form negative ions by gaining or accepting electrons.
In fact, non-metals are known as electronegative elements because they can from negative ions by gaining electrons.
There are 11 non-metallic gases. Out of these only bromine is liquid and the rest are in solid state.
Some of the examples of non-metals are: carbon, Sulphur, Phosphorus, Silicon, Hydrogen, Oxygen, Nitrogen, Chlorine, Bromine, Iodine, Helium, Neon and Argon.
The most abundant non-metal in the earth’s crust is oxygen.
Hydrogen is used in the hydrogenation of vegetable oil.
PHYSICAL PROPERTIES OF METALS
Metals are malleable, that is metals can be beaten into thin sheets with a hammer without any breakage. Gold and silver metals are some of the best malleable metals.
Metals are ductile which means that metals can be drawn or stretched into thin wires.
Gold is the most ductile metal.
Metals are good conductors of heat: Silver is the best conductor of heat among all the metals.
Metals are good conductors of electricity: Silver metal is the best conductor of electricity. And this is why electric wires are made of copper and aluminium metals.
Metals are lustrous (or shiny), and can be polished:-Any shining surface is called as lustrous. For example, gold, silver and copper are shiny metals and they can be polished. The property of a metal of having a shining surface is called ‘metallic lustre’. The shiny appearance of metals makes them useful in making jewellery and decoration piece.
For example, gold and silver are used for making jewellery because they are bright and shiny. The shiny appearance of metals makes them good reflectors of light. Silver metal is an excellent reflector of light. This is why it is used in making mirrors.
The metals lose their shine or brightness on keeping in air for a long time and acquire a dull appearance due to the formation of a thin layer of oxide, carbonate or Sulphide on their surface this is due to the slow reaction of the various gases present in air.
This process is known as corrosion. To remove the outer corroded layer, we rub the dull surface of a metal object with a sand paper and then the metal object becomes shiny and bright once again.
Metals are generally hard, Except for sodium and potassium which are soft metals. In fact, Sodium metal can be easily cut into smaller pieces.
Metals are solid at room temperature, except for mercury which is a liquid metal
Most of the metals like iron, copper, aluminium, silver and gold, etc., are solids at the room temperature. An exception happens in mercury, which remains at liquid state in the room temperature.
Metals have high melting points and boiling points, except for sodium and potassium metals which have low melting and boiling points.
Metals have high densities except for sodium and potassium metals which have low densities
Metals are sonorous. That is, metals make a sound when hit with an object
PHYSICAL PROPERTIES OF NON-METALS
Non-metals are neither malleable nor ductile. Non-metals are brittle i.e. it break easily.
Non-metals do not conduct heat and electricity. An exception occurs in the case of Carbon (in the form of graphite), which conducts electricity.
Non-metals are not lustrous. They are dull. An exception occurs in the case of Iodine which possesses having a lustrous appearance.
Non-metals are generally soft, except for diamond which is an extremely hard non-metal.
Non-metals are not strong. They are easily broken.
Non-metals can be solid, liquid or gases at room temperature
Non-metals have comparatively low melting points and boiling points, except for diamond which is a non-metal having a high melting point and boiling point.
Non-metals have low densities, that is, non-metals are light substances
Non-metals are non-sonorous, i.e. they do not produce sound when hit with an object
Non-metals have many different colours.
For example, sulphur is yellow, phosphorus is white or red, graphite is black, and chlorine is yellowish-green whereas hydrogen and oxygen are colourless.
