Introduction

Various types of substances are found around us. Some of them are soft, some are hard, some are pure and some are impure. They may be found in different states. Among them, pure substances are known as elements. Till now, 118 elements have been discovered. These elements are divided into three types on the basis of their properties. They are metals, non- metals and metalloids. The majority of the elements are metals. Metals are hard, good conductor of heat and electricity, malleable and ductile. Some of the common examples of metals are copper, silver, gold, aluminium etc. Non- metals are non- malleable and non- ductile. They are soft in nature and are the bad conductor of heat and electricity. Some of the common examples of non- metals are carbon, sulphur, iodine, nitrogen etc. There are also some elements that show both the properties of metals and non- metals. These elements are known as metalloids. They conduct heat and electricity better than non- metals but not as good as metals. Some of the common examples of metalloids are silicon, germanium and antimony.

Metals

Metals are opaque, lustrous elements that are good conductors of heat and electricity. Most of the metals are malleable and ductile. Most of them are hard. When we hit the metals, it produces tinkling sound. We use metals in our daily life activities. Metals are used for making furniture, utensils, jewellery, etc. They are used in transportation, communication, construction, industries, electrical power production, and distribution etc. Some of the common examples of metals are gold, silver, iron, aluminium, copper, brass, etc. Most of the metals exist in the solid state at room temperature except some metals like mercury, gallium etc. These metals exist in the liquid state.

Properties of Metals

• They are the good conductor of heat and electricity.
• They have a shiny appearance.
• They have high melting point.
• Most of them are malleable and ductile
• When we hit metals, it produces tinkling sound

Non- Metals

Non- metals are those elements that lack metallic properties. They cannot be beaten into thin sheets and cannot be folded and cannot be drawn into thin wires like metals. They are the bad conductor of heat and electricity but graphite though being a non- metal can conduct heat and electricity. They are non- lustrous. They are also used in our daily life activities like used to make medicines, utensils, containers, etc. Some of the common examples of non- metals are carbon, sulphur, phosphorus, chlorine etc.

Properties of Non- Metals

• They are non- malleable and non- ductile.
• They do not conduct heat and electricity.
• They are soft in nature
• When we hit non- metals, they do not produce tinkling sound.
• They are found in the solid, liquid and gaseous state.

Alloys

An alloy is a defined as a metal made by combining two or more metallic elements. It is made from the combination of two or more metals or metals and non- metals. We use alloys in our daily life activities. More than 90% of metals used are in the form of alloys. About the preparation of alloys, two or more than two metals are mixed in their molten state and then cooled to obtain the solid product as alloys. The common alloys that are used in our daily life activities are given below,

• Stainless steel: Mixture of iron, chromium and carbon
• Bronze: Mixture of copper and tin
• Brass: Mixture of copper and zinc
• Steel: Mixture of iron and carbon

The properties of alloys are different from the properties of its components. The physical and chemical properties of an alloy can be modified by heat treatment and mechanical working. The main purpose of making alloys is given below,

• To improve the strength and hardness of metals.
• To lower the melting point.
• To prevent the metals from rusting and corrosion.
• To improve the appearance of the metal and get different colours.

Some Useful Alloys

• Brass: It is an alloy composed of copper and zinc. It is also known as copper alloy as copper is the main component. Usually, the brass is yellow in colour. It is a malleable and good conductor of heat. Rusting does not occur in brass. It is used for making cooking utensils, ornaments, bearings, musical instrument, gears, knobs, locks, coins, statue, etc. It is also used in decoration as it has gold- like appearance.
• Bronze: An alloy or mixture of copper and tin is known as bronze. It is faint yellow in colour. It has a low melting point and does not get rust. It is mainly used for making household utensils as utensils made of bronze looks attractive. It is also used for making pitchers, statues, gears, bells, valves, weapons, medals, musical instrument, etc.

Some Useful Non- Metals

• Sulphur: It is a non- metallic chemical element with symbol S and atomic number 16. It is the thirteen most abundant element in the earth's crust. It is used for making gunpowder, firecrackers, matches, etc. It is also used in the manufacture of fertilisers and other chemicals. It is used as medicines for curing skin diseases.
• Iodine: It is a non- metallic chemical element with a symbol I and atomic number 53. Our body also need some amount of iodine. Our body needs iodine to make thyroid hormones as it controls the body's metabolism and many other important functions. If there is a deficiency of iodine, our thyroid gland swells and enlarges. It is also used in photography, iodex and in medical treatment of thyroid cancer. It is mostly used as disinfectant for external wound, antiseptic for the treatment of minor cuts, etc.