Metals and Non-Metal

Elements can be classified as metals and non-metals. Metals have the tendency to lose electron and form cation. Metals are electropositive elements. Most of the metals are solid under normal conditions of temperature and pressure except mercury. Metals are lustrous, malleable, ductile and are good conductors of heat and electricity. Metals are sonorous in nature. The arrangement of metals in a vertical column in the decreasing order of their reactivity is called activity series. The most reactive metal is placed at the top, whereas the least reactive metal is placed at the bottom. A more reactive metal displaces a less reactive metal from its salt solution. Metals combine with oxygen to form basic oxides. Aluminium oxide and zinc oxide show the properties of both basic as well as acidic oxides. These oxides are known as amphoteric oxides. Different metals have different reactivities with water and dilute acids. Metals above hydrogen in the activity series can displace hydrogen from dilute acids. Metals and Non-metals Non-metals Elements can be classified as metals or non-metals on the basis of their properties. Non-metals have the tendency to gain electrons and form anions. Some of the examples of non-metals are carbon, sulphur, iodine, oxygen, hydrogen, etc. The non-metals are either solids or gases except bromine which is a liquid. They are electronegative elements. Non-metals have properties opposite to that of metals. They are neither malleable nor ductile. Non-metals are bad conductors of heat and electricity, except for graphite, which conducts electricity. Non-metals are neither malleable nor ductile. They are soft and brittle. The oxides of non metals are either acidic or neutral. Acidic oxides of non-metal dissolve in water to give acid. Non-metals do not displace hydrogen from dilute acids. They react with hydrogen to form hydrides. The compounds formed in this manner by the transfer of electrons from a metal to a non-metal are known as ionic compounds or electrovalent compounds. The bond formed between cation and anion is called ionic bond. Ionic compounds are crystalline solids. They are brittle and break into pieces on applying force. Ionic compounds are soluble in water and insoluble in organic solvents like benzene, alcohol, etc. They do not conduct electricity in solid state but in aqueous solution or in molten state, they conduct electricity. Metals and Non-metals Metallurgy The earth crust is the major source of metals. Seawater also contains some soluble salts such as sodium chloride, magnesium chloride, etc. Metal bearing substances, found in the earth’s crust, are called minerals. The minerals from which metals can be obtained on a commercial scale are called ores. In other words, the minerals from which metals can be extracted profitably are called ores. Metallurgy is the process of extracting metals from their ores and refining them. The various steps used in metallurgy are concentration or dressing of the ore, conversion of the enriched ore into the oxide of metal, extraction of metal from the metal oxide, refining or purification of the metal. Earthly impurities like silica, mud, rock pieces and clay associated with the ore are called gangue or matrix. Science Class 10 Chapter– 3 Metals and Non-metals Alloys The properties of any metal can be changed if it is mixed with some other substance. The substance added may be a metal or a non-metal. An alloy is a homogeneous mixture of two or more metals, or a metal and a non-metal. Brass is an alloy of copper and zinc. Bronze is an alloy of copper and tin. Solder is an alloy of lead and tin. Amalgam is an alloy of mercury with other metal. 22 carat gold is used for making ornaments. It means that 22 parts of pure gold is alloyed with 2 parts of either copper or silver. Alloys are harder than their constituents but less ductile and malleable. Alloys are resistant to corrosion. The melting point of an alloy may be higher or lower than any of its constituents. The properties of an alloy are much more improved and pronounced than those of its constituents. Science Class 10 Chapter– 3 Metals and Non-metals Corrosion When the surface of a metal is attacked by air, moisture or a chemical substance, the metal corrodes and the phenomenon is known as corrosion. It is also called weeping of metal. Metals under attack react with oxygen and water vapours to form metal oxides. A reddish brown coloured layer is formed on the surface of iron due to corrosion. This layer is known as rust and corrosion of iron is known as rusting. Water and air both are essential for rusting of iron. In the absence of any one of these rusting will not take place. The presence of salts, acids, carbon dioxide, and sulphur dioxide in water enhances the process of rusting of iron. The various methods used for prevention of corrosion are by surface coating, galvanisation, electroplating, alloying with metals.

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