METALS AND NON-METALS

METALS usually show some or all of the following properties:

• They have a lustre (shine).
• They have silvery-grey or golden-yellow colour.
• They conduct heat and electricity.
• They are ductile (can be drawn into wires).
• They are malleable (can be hammered into thin sheets).
• They are sonorous (make a ringing sound when hit).

Examples of metals are gold, silver, copper, iron, sodium, potassium etc. Mercury is the only metal that is liquid at room temperature.

• In general, metallic oxides are basic in nature.
• Sodium metal is very reactive. It reacts vigorously with oxygen and water. A lot of heat is generated in the reaction. It is, therefore, stored in kerosene. Some other metals might not react that vigorously. For example, iron reacts with water slowly.
• Metals react with acids and bases to produce hydrogen gas that burns with a ‘pop’ sound.
• More reactive metals displace less reactive metals from their compounds in aqueous solutions.

On the basis of reactivity, we can group the metals into the following three categories –  Metals of low reactivity;  Metals of medium reactivity;  Metals of high reactivity. Different techniques are to be used for obtaining the metals falling in each category.

NON-METALS usually show some or all of the following properties:

• They display a variety of colours.
• They are poor conductors of heat and electricity.
• They are not lustrous, sonorous or malleable.

Examples of non-metals are hydrogen, oxygen, iodine, carbon (coal, coke), bromine, chlorine etc.

• Generally, oxides of non-metals are acidic in nature.
• Generally, non-metals do not react with water though they may be very reactive in air. For example, phosphorus is a very reactive non-metal. It catches fire if exposed to air. To prevent the contact of phosphorus with atmospheric oxygen, it is stored in water.
• Non-metals generally do not react with acids. Reactions of non-metals with bases are complex.

Some elements have intermediate properties between those of metals and non-metals, they are called METALLOIDS; examples are boron, silicon, germanium etc.

Exceptions–

1. All metals except mercury exist as solids at room temperature.
2. Metals generally have high melting points but gallium and caesium have very low melting points. These two metals will melt if you keep them on your palm.
3. Iodine is a non-metal but it is lustrous.
4. Alkali metals (lithium, sodium, potassium) are so soft that they can be cut with a knife. They have low densities and low melting points.