General Science for SSC Exam

About Metal and Non-Metal

METAL & NON-METAL:

1. All the materials found in the earth's crust are made up of chemical elements.

2. All these elements can be broadly divided into two classes:

Metals and Non-metals.

Note : Out of 117 elements 83 are naturally occuring. Out of total 117 elements about 24 are non-metals and rest are metals.

3. Physical Properties of Metals

• Metals, in their pure state, possess a shining surface(metallic lustre). Freshly cut metals have a bright metallic lustre.

• Metals are solid at room temperature. Mercury is the only metal that is liquid at room temperature.

• Metals are generally hard and strong. But metals like sodium and potassium are exceptionally very soft and can be cut with a knife.

• Metals have high melting and boiling points. Sodium,potassium, gallium and mercury have low melting and boiling points.

• Metals are good conductors of heat. Silver, followed by copper and aluminium, is the best conductor of heat. These days, cooking vessels and other utensils are made up of copper and aluminium.

• Metals are also good conductors of electricity. Silver, followed by copper, gold and aluminium, is the bestconductor of electricity. Copper and aluminium are used for making electrical wires.

• Metals are sonorous. They make a ringing sound when struck.

• Metals are usually malleable. They can be hammered into thin sheets and rolled into different shapes without breaking. Gold and silver are the most malleable metals.

• Metals are generally ductile. They can be easily drawn into wires. Gold and silver are most ductile metals. Copper wires are used for electrical purposes.

• Metals have high tensile strength, i.e. they can hold heavy loads without breaking.

• Metals have high densities i.e. they are heavy in nature. Sodium and potassium metals are exceptions as they have low densities and float on water.

4. Corrosion is the process of slowly eating away of metal due to attack of atmospheric gases and water on the surface of metal. The most common example of corrosion is the rusting of iron.

Rusting: Rusting is the corrosion of iron on exposure to atmosphere

Non-metals are quite abundant in nature. They are main constituent of atmosphere.

• Oxygen, nitrogen and noble gases are present in the air.

• Non-metals are also present in large amounts in oceans.

• Hydrogen and oxygen are present as water and chlorine is present as chlorides in the oceans.

• Oxygen, silicon, phosphorus and sulphur are present in the earth's crust.

6. Physical Properties of Non-metals:

• Non-metals are either solids or gases at room temperature. Bromine is the only liquid non-metal at room temperature.

• Non-metals are soft. Phosphorus is so soft that can be cut with a knife. Diamond, an allotrope of carbon, is the hardest known substance.

• Non-metals have low tensile strength, i.e. they are not strong and break easily.

• Non-metals are non-lustrous and have a dull appearance. Graphite, an allotrope of carbon and iodine have shining lustrous surfaces.

• Non-metals are non-malleable and non-ductile. They cannot be hammered into sheets or drawn into wires. These are brittle solids. When non-metals like sulphur, are hammered or stretched, they break into pieces.

• Non-metals are non-conductors or bad conductors of heat and electricity. Gas carbon and graphite are good conductors of heat and electricity.

• Non-metals are non-sonorous i.e. do not make a ringing sound when struck.

• Non-metals usually have low densities