Metals and Nonmetals for (2009-2010)

• Metals are obtained at cathode. Metals release electron and form positive ions. During electrolysis the metal ions move towards negative electrode i.e. cathode. They get electrons there and change into metals.
• Calcium and magnesium start floating when react with water because bubbles of hydrogen gas formed stick to the surface of the metals and the metals along with H₂ gas become lighter than water.
• Metals like Na, K, Li are kept immersed in kerosene oil because they are highly reactive and can catch fire when kept in open. So to protect them and to prevent accidental fires they are kept immersed in kerosene.
• Nonmetal phosphorus is kept immersed under water because it is highly reactive and can react with air to form its oxides.
• Electric wires are coated with PVC or plastic to protect ourselves from severe shocks as metallic wires are good conductor of electricity.
• Metals are used to make cooking vessels because they are good conductors of heat
• The electrical conductivity and melting point of an alloy is less than that of pure metal.
• Tungsten is used exclusively for filament of electric bulbs because of its high melting point and high resistance
• Carbon can reduce copper oxide to copper as carbon is a strong reducing agent but cannot reduce calcium oxide to calcium because calcium is more reactive than carbon and has great affinity for oxygen than carbon.
• Aqueous solution of sodium chloride is not used in the electrolysis of sodium metal because sodium obtained at cathode will react with water to form sodium hydroxide and hydrogen gas.

2Na + H₂O(l) 2NaOH + H₂