Materials: Metals and Non-Metals Notes

• There are about 118 chemical elements known at present of which only 98 elements are known to occur naturally on earth.
• Based upon their properties elements are classified into two main groups :

      1.  Metals

      2. Nonmetals

Physical properties of metals:

Reaction of metals with oxygen:

• Metals react with oxygen producing respective oxides.
• Metals like sodium (Na) and potassium (K) are some of the most reactive metals.
• Sodium metal reacts with the oxygen of the air at room temperature to form sodium oxide. The reaction is vigorous hence sodium is stored under kerosene to prevent its reaction with oxygen, moisture and carbon dioxide.
• Rusting of iron, burning of Mg ribbon in air
• In both processes oxides are formed.

Reaction:

Reaction of metals with water

• Metals react with water forming hydroxides.

Example:

• Sodium reacts with water forming sodium hydroxide and Hydrogen, heat is released.