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| Summary
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- An electrolyte is a compound (salt, acid or base),
which in solution or in a molten state conducts an electric current and is
simultaneously decomposed by it
- Electrolytes are ionised into
electrically charged ions, which carry the current
- 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
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Metals and non-metals are characterized by distinctly different physical and
chemical properties
- Main physical properties of metals are:
lustrous, malleable, ductile, hard, dense, high boiling and melting points
- Metals are also good conductors because they have free electrons, have 1 to 3 electrons in the outermost shell of their atoms and tend to lose electrons and form cations
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Non-metals exist in two of the three states of matter at room temperature,
are brittle neither malleable nor ductile, poor conductors of heat and
electricity and have a tendency to gain or share electrons with other atoms
- Metals occupy the groups on the left of periodic table and are largely classified as alkali metals (group IA) alkaline earth metals (group IIA) and transition metals (elements between group IIA and IIIA)
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Metals and non-metals combine to form electrovalent or ionic compounds by
transfer of electrons between themselves
- Reaction of metals with air to form oxides and with water and acids to liberate hydrogen gas can be summarized as follows:
- The reactivity series of metals places the most reactive metal
on the top and the least reactive metal at the bottom
- Metals occur
in the Earth's crust either in the native state (gold, platinum) or in the
combined forms as minerals
- Minerals that can be profitably used as a source of some desired materials are termed as ores. The earthly impure material present in an ore is known as gangue.
- There are several methods for concentration of ores like hydraulic washing, froth-floatation, and magnetic separation or chemical processes. The nature of the ore determines the choice of a method.
- Concentrated ore is subjected to heating for extracting less reactive
metals in the reactivity series of metals
- Moderately reactive metals in the reactivity series of metals are roasted or calcined so as to convert to the oxide
form and then further reduced with coke or carbon monoxide
- Metals above carbon in the activity series are extracted by electrolysis. They are the most reactive metals.
- The metals extracted by all the above processes are finally refined to make them pure by several different methods like liquation, distillation, and electrorefining
- Corrosion is an oxidation reaction which harms metals like iron and steel. Aluminium, copper and silver also react but to a lesser extent. Group 1 alkali metals rapidly corrode in air.
- Some method of preventing corrosion of metals are painting, greasing,
putting oil on the surface, sacrificial protection, alloying, galvanizing
and electroplating
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