Elements can be classified into the following two groups depending on their physical and chemical properties:
The elements which are hard, shiny can be beaten into sheets, drawn into wires and are good conductor of heat and electricity are generally metals.
For example: iron, copper, gold etc.
In nature most metals occur in the combined state as minerals and they are reactive.
Only a few unreactive metals like gold, silver, platinum are found as free metals in the earth’s crust.
Minerals from which metals can be profitably extracted are called ores.
For example: calcium occurs in limestone (calcium carbonate) or iron in the ore haematite.
The elements which are brittle, dull cannot be beaten into sheets or drawn into wires and are poor conductors of heat and electricity are generally non-metals.
For example: oxygen and nitrogen occur in free state in air and in combined state in earth’s crust. Sulphur occurs both in free and the combined state in earth’s crust.
The noble gases, helium, neon, argon, krypton, xenon occurs only in Free State.
Physical properties of Metals:
Metals are solids at room temperature, except mercury, which is liquid at room temperature.
They are generally hard and strong but sodium and potassium are soft solids and can be cut with a knife.
They are good conductor of heat and electricity. Copper is the best conductor of electricity followed by gold and aluminium.
Metals such as gold, silver and copper all have lustre, that is they have an ability to shine and reflect light. Therefore they are lustrous.
The property by virtue of which metal can be beaten into sheets is called malleability. We use aluminium foil to pack food.
The property by which metals can be drawn into wires is called ductility. Metals like copper, silver and aluminium can be drawn into wires.
Metals are sonorous. They produce sound when struck.
With the exceptions of sodium, potassium and mercury most of the metals have high melting and boiling point.
Metals have high densities.
Most metals have high tensile strength.
Physical properties of Non-metals:
Non-metals are gases or solid at room temperature, except bromine which is liquid at room temperature.
Non-metals do not have lustre except iodine and graphite.
They are bad conductor of heat and electricity.
Non-metals are brittle that is they are neither malleable nor ductile.
They usually have low densities.
Non-metals have low melting point and boiling point.
Non-metals are non-sonorous.
The elements which possess the properties of metals and non-metals are called metalloids.
For example: boron, silicon, germanium, tellurium, arsenic and antimony are metalloids.
Chemical properties of Metals and Non-metals:
etals along with hydrogen (a non-metal) are arranged in order to their activity in a series, called the activity series.
Reaction with oxygen:
Reaction of metals with oxygen:
etals react with oxygen under different conditions to form basic oxides. These basic oxides react with water to form bases which turn red litmus into blue.
Sodium and potassium react with oxygen vigorously at room temperature.
4Na + O2 ---> 2Na2 O
To prevent this oxidation, sodium and potassium are stored under kerosene.
agnesium reacted with oxygen only if ignited. It gives a bright dazzling flame and forms a white powder of magnesium oxide.
2Mg + O2 ----> 2MgO
Iron metal does not burn in dry air even on strong heating. In moist air, iron get oxidise to form iron oxide (rust)
4Fe + 3O2 ------> 2Fe2 O3
Fe2 O3 + nH2 O ------> Fe2 O3 nH2 O
Reaction of non-metals with oxygen:
Non-metals react with oxygen to form acidic or neutral oxides.
C + O2 ----> CO2
S + O2 -----> SO2
Other oxides like carbon monoxide (CO) and nitrous oxide (N2O) are neutral.
Reaction with water:
Reaction of metal with water:
etal react with water to form oxides or hydroxides along with hydrogen. Different metals react at different temperature.
Sodium, potassium and calcium react vigorously with cold water to form metal hydroxides.
2Na + 2H2O -----> 2NaOH + H2
etal from magnesium to iron react with steam (but not water) to form metal oxide and hydrogen gas.
2Mg + H2O -----> 2MgO + H2
Tin, lead, copper, silver and gold do not react with water or steam.
Reaction of non-metal with water:
Non-metals do not generally react with water.
Reaction with dilute acids:
Reaction of metals with dilute acids:
etals react with dilute acids to form their salt and liberate hydrogen gas. The evolution of hydrogen gas can be tested by bringing a burning splinter near the mouth of the test tube. Hydrogen gas will put off the splinter with a pop sound.
2Na + 2HCl ------> 2NaCl + H2
Zn + H2SO4 ------> ZnSO4 + H2
etals below hydrogen (copper, silver, gold and platinum) do not react with dilute acids as they are less reactive than hydrogen. So they cannot displace hydrogen from dilute acids.
Reaction of non-metals with dilute acids:
Non-metals do not react with dilute acids.
A more reactive metal displaces a less reactive metal from its compound in aqueous solution. Such a reaction is known as displacement reaction.
For example: When iron nail put in copper sulphate solution then colour of solution changes from blue to light green and a reddish brown coating of copper is seen on iron nail.
Fe + CuSO4 ---> FeSO4 + Cu
Iron copper sulphate iron suphate copper
Iron sulphate + copper no reaction
Because copper is less reactive than iron so cannot displace it.
Uses of metals and non-metals:
Uses of metals:
Copper and aluminium are used to make wires for carrying electric currents.
Zinc is used for galvanising iron to protect iron from rusting.
Silver, gold and platinum are used make jewellery.
Iron, copper and aluminium metals are used to make utensils for cooking and for manufacturing machines parts.
Mercury is used in thermometer.
Lead is mainly used for making electrodes for automobile batteries and for making alloys.
Uses of non-metals:
Hydrogen is used in manufacture of ammonia, industrial chemicals.
Liquid nitrogen is used in refrigerant, in storing human organs at low temperature.
Sulphur is used in manufacture of sulphuric acid, sulphur dioxide gas, sulphur drugs etc.
Sulphur is used for vulcanisation of rubber and making gunpowder.
Phosphorus is used in the manufacture of fertilisers.
Silicon is used for making semiconductors foe which microchips are made.
Chlorine is used for disinfecting drinking water.
Oxygen is used in breathing support system for patients.
Fill in the blanks:
Metal react with oxygen to produce ................oxides and non-metal react with oxygen to produce................oxides.
The presence of .............. and ..................are necessary for iron to rust.
...................is used for making X-ray shields.
.....................non-metals is used in fluorescent bulbs to display advertisements.
....................element is used for making pencil lead.
.....................is the only non-metals that exist as liquid at room temperature.
The property of metals by which it can be beaten into sheets is called.................
.....................metal can be cut with knife.
......................non-metal is used for vulcanisation of rubber.
.......................metal is used in processed food packaging.
Process of coating metals with zinc is called.......................
Elements that possess properties of both metals and non-metals are called.............
....................is a pure chemical substance consisting of only one type of atoms.
Metal react with dilute acids to form...................... and.......................
Salt, hydrogen gas
Why is gold used for making jewellery?
Gold does not easily react with other substances. It is an unreactive metal and once polishes, it retains their shine for a long time, therefore, it is used for making jewellery.
What do you mean by corrosion?
Corrosion is used to describe the process by which minerals such as metals are slowly eaten away when exposed to air and moisture.
No gas is released when sulphur is added to dilute HCl?
No gas is releases when sulphur is added to dilute HCl because non-metals do not react with dilute HCl and sulphur is a non-metal.
Why are electrical cables made from copper?
Since copper is a good conductor of electricity, it is used in electrical cables.
Why do copper vessels develop a greenish layer when exposed to moist air?
Copper vessel gets corroded in the presence of moist air that is carbon dioxide and water to form green coating of a substance called basic copper carbonate.
Which non-metal is considered to be backbone of the electronics industry?
Silicon is considered to be the backbone of electronics industry.
Why is sodium metal stored under kerosene?
Sodium metal which react vigorously with the oxygen present in air at room temperature to form sodium oxide. Hence, sodium is stored under kerosene to prevent its reaction with oxygen and moisture present in air.
Write the difference between metal oxides and non-metal oxides?
Metal oxides formed are basic in nature, when dissolved in water they form bases which turn red litmus into blue whereas non-metal oxides are acidic in nature, when dissolve in water they form acids which turn blue litmus into red.
Silver is more likely to tarnish near a petroleum refinery than in a place far away? Explain why?
Silver does not get easily corroded in unpolluted air, however, if the air is polluted with sulphur compounds such as hydrogen sulphide then silver reacts with it to form a black coating of silver sulphide.
What are noble metals?
Silver and gold are present at the bottom of the reactivity series of metals. They are unreactive metals and do not react with water, acids and alkalis. They therefore, occur n free state in nature. So they are noble metals.