Earth is an abundant source of materials. The air we breathe, the water we drink, stones and rocks, almost everything that is around us, are all useful to man for some purpose or the other.
Metals are solids at room temperature with the exception of mercury and gallium, which are liquids at room temperature.
Metals are very reactive. Metals tend to loose electrons easily and form positively charged ions.
Although most metals are usually electropositive in nature and lose electrons in a chemical reaction they do not react with the same vigour or speed. Metals display different reactions towards different substances.
We are familiar with the fact that the atoms of all elements, except noble gases, have an incomplete outermost shell.
Metals and their compounds are found in earth as natural elements known as minerals. Ores are minerals from which metals are extracted profitably and conveniently.
The compounds of various metals found in nature as ores are mixed with impurities like sand and rock.
Ore is an impure metal containing large amount of sand and rocky material. The impurities like sand, rocky materials, limestone, mica etc present in the ore is called gangue or matrix.
Metals that are low in the activity series are very un-reactive. The oxides of these metals can be reduced to metals by heating alone.
Metals such as iron, zinc, lead, copper, etc., are in the middle of the reactivity series. These are moderately reactive metals and are usually present as sulphides or carbonates.
The oxide obtained by calcination or roasting is then reduced by either carbon or hydrogen.
Metals such as sodium, magnesium, calcium, aluminium high up in the reactivity series are very reactive and cannot be obtained from their compounds by heating with carbon.
Most metals obtained by the reduction process are not very pure. These have to be further refined or purified. Purification of the metal is the last step in metallurgy.
We have learnt that metals that are chemically active get corroded in the presence of a moist atmosphere.
Charged ions move towards the oppositely charged electrodes to give up their electric charge and become atoms; these are either liberated or deposited at the electrodes.