2. Physical properties of metals :-
Metals are solids. (except mercury)
Metals are hard. (except Lithium, Potassium, Sodium)
Metals have metallic lustre. (shine)
Metals are malleable. (can be beaten into thin sheets)
Metals are ductile. (can be drawn into wires)
Metals have high melting points. (Gallium and Ceasium
have low melting points. They melt in the palm of the hand)
Metals have high boiling points.
Metals are good conductors of heat. ( Best conductors are
silver and copper. Poor conductors are Lead and Mercury)
Metals are good conductors of electricity. ( Best
conductors are Silver and Copper)
Metals are sonorus. (produce sound when beaten)
Mercury expands significantly for the slightest change in
temperature.
3. Physical properties of non metals :-
Non metals may be solids, liquids or gases. (Solids
– Carbon, Sulphur, Phosphorus etc. Liquid –
Bromine, Gases – Oxygen, Hydrogen, Nitrogen
etc.)
Non metals are soft. (except diamond which is the
hardest natural substance)
Non metals do not have lustre.(except iodine
cryatals)
Non metals are not malleable.
Non metals are not ductile.
Non metals which are solids and liquids have low
melting points and boiling points.
Non metals are bad conductors of heat.
Non metals are bad conductors of electricity.
(except graphite)
Non metals are not sonorus.
4.
5. Chemical properties of metals :-
i) Reaction with oxygen :-
Metals react with oxygen to form metal oxides.
When copper is heated it combines with oxygen to form copper oxide.
2Cu + O2 2CuO
When aluminium is heated it combines with oxygen to form aluminium
oxide. 4Al + 3O2 2Al2O3
Some metal oxides are basic oxides because they react with water to
form bases.
4Na + O2 2Na2O
Na2O + H2O 2NaOH
K + O2 K2O
2KOH
K2O + H2O
Some metal oxides show acidic and basic properties. They are called
amphoteric oxides. Eg :- Aluminium oxide, Zinc oxide etc.
2AlCl3 + 3H2O
Al2O3 + 6HCl
(basic)
Al2O3 + NaOH
(acidic)
NaAlO2 + H2O
(Sodium aluminate)
6. The reactivity of different metals with oxygen is different :-
Metals like potassium and sodium react vigorously with
oxygen and catch fire if kept in open. Hence they are
stored in kerosene to prevent burning.
If magnesium is heated, it burns with a bright flame.
If iron is heated it glows brightly.
If copper is heated it does not burn but forms a black
coating of copper oxide.
Silver and gold does not react with oxygen even at high
temperature.
Some metals like magnesium, aluminium, zinc, lead etc.
forms an oxide layer over it which prevents further
oxidation. They are called self protecting metals.
7. Reaction with water :-
Metals react with water to form metal oxides or metal hydroxides and
hydrogen.
2Na + 2H2O 2NaOH + H2
2K + H2O
Ca + H2O
2KOH + H2
Ca(OH)2 + H2
2Al + 3H2O
3Fe + 4H2O
Al2O3 + H2
Fe2O3 + 4H2
The reactivity of different metals with water is different :-
Sodium and potassium react violently with cold water to form
sodium hydroxide and hydrogen and catches fire.
Calcium reacts less violently with water to form calcium hydroxide
and water and does not catch fire.
Magnesium reacts only with hot water to form magnesium
hydroxide and hydrogen.
Metals like aluminium, iron and zinc react only with steam to form
the metal oxides and hydrogen.
Metals like lead, copper, silver and gold do not react with water.
8. Reaction with acids :-
Metals react with dilute acids to form salts and
hydrogen.
Mg + 2HCl MgCl2 + H2
2Al + 6 HCl 2AlCl3 +3H2
Zn + 2HCl ZnCl2 + H2
Fe + 2HCl FeCl2 + H2
The reactivity varies from metal to metal. For the above
metals the decreasing order of reactivity is Mg > Al > Zn > Fe.
Copper, silver and gold do not react with dilute HCl.
Hydrogen gas is not evolved when metals react with nitric
acid (HNO3) because it is a strong oxidising agent and it
oxidises the H2 produced to water and is itself reduced to
oxides of nitrogen. Mn and Mg react with dil. Acid to produce
hydrogen gas.
3Cu + 8HNO3 3Cu(NO3)2 + 4H2O + 2NO2
9. Reaction of metals with metal salt solutions :-
A more reactive metal displaces a less reactive metal from its salt
solution. (Displacement reaction)
Magnesium displaces copper from copper sulphate solution.
Mg + CuSO4 MgSO4 + Cu
Zinc displaces copper from copper sulphate solution.
Zn + CuSO4 ZnSO4 + Cu
Iron displaces copper from copper sulphate solution
Fe + CuSO4 FeSO4 + Cu
after 15 – 20 minutes
10. Reactivity series of metals :-
The arranging of metals in the decreasing order of their
reactivity is called reactivity series of metals.
K - Potassium
Na - Sodium
Ca - Calcium
Mg - Magnesium
Al - Aluminium
Zn - Zinc
Fe - Iron
Pb - Lead
H - Hydrogen
Most reactive
Reactivity decreases
Cu - Copper
Hg - Mercury
Ag - Silver
Au - Gold Least reactive
11. How do metals an non metals react ?
Metals :- Metal lose electrons and become positive ions. So
they are called electropositive elements.
Eg :- The atomic number of sodium is 11, its electronic configuration is
2,8,1, it has 1 valence electron. It loses 1 electron and forms a sodium
ion Na +
Non metals :- Non metal gain electrons and become negative ions. So
they are called electro negative elements.
Eg:- The atomic number of chlorine is 17, its electronic configuration is
2,8,7, it has 7 valence. It gains 1 electron and forms a chloride ion Cl -
12. Formation of Magnesium chloride molecule – MgCl2
Mg Mg 2+ + 2e -
AN = 12
EC = 2,8,2 2,8
2Cl+ 2e - 2Cl -
AN = 17
EC = 2,8,7 2,8,8
Mg + Mg MgCl2
The AN of Mg is 12, its EC is 2,8,2, it has 2 valence electrons, it loses 2
electrons to form Mg 2+ . The AN of Cl is 17, its EC is 2,8,7, it has 7
valence electrons, it gains 1 electron to form Cl -. Then the attraction
between Mg 2+ ion and 2 Cl - ions results in the formation of Magnesium
chloride molecule – MgCl .
.
.
x
xx
x
xx
xx
x x
x
Cl x
x Cl x
2+
-
x x
xx
-
x x
x
xx
xx
.Cl
Cl x
xx
.
13. Ionic compounds (Electrovalent compounds) :-
Ionic compounds are compounds formed by the transfer of
electrons from a metal to a non metal.
Properties of ionic compounds :-
i) They are formed by the transfer of electrons and are made up of
ions.
i) They are crystalline solids.
ii) They have high melting points and boiling points.
iii) They are soluble in water but insoluble in organic solvents (like
petrol, kerosene etc.)
iv) They conduct electricity in molten state or in solution.
14. Occurrence of metals :-
Some metals like gold, silver, platinum etc are found in the free
state in the earth’s crust because they are least reactive. Most metals
are found as oxides, carbonates, sulphides, halides etc.
Minerals :- Minerals are elements or compounds which occur
naturally inside the earth’s crust.
Ore :- The mineral from which metals can be extracted profitably and
easily is called Ore.
Gangue :- Gangue is the impurities present in the ore like rock
particles, sand particles, clay particles etc.
Extraction of metals from their ores :-
Metals are extracted from their ores in three main steps. They are :-
i) Concentration of the ore (Enrichment of the ore).
ii) Reduction to the metal.
iii) Refining (Purification of the metal).
Concentration of the ore :- is the removal of gangue (impurities)
from the ore by different methods.
15.
16. Extraction of metals low in the activity series :-
Metals which are low in the activity series can be
reduced to the metals by heating in the presence of oxygen
(Roasting).
Eg :- Mercury is obtained from its ore Cinnabar (HgS) by
heating in the presence of oxygen. When it is heated in the
presence of oxygen it is first converted into mercuric oxide
(HgO) and on further heating it is reduced to mercury.
2HgS + 3O2 2HgO + 2O2
2HgO 2Hg + O2
2CuS + 3O2
2Cu2O + Cu2S
2Cu2O + 2SO2
6Cu + SO2
Copper is obtained from its sulphide ore (CuS) by
heating in the presenceofoxygen
heat
heat
heat
heat
17. Extraction of metals in the middle of the activity series :
Metals in the middle of the activity series like Zn, Fe, Pb, are found as
oxide, sulphide or carbonate ores.
It is easier to obtain metals from their oxides than from their
sulphides or carbonates. So non oxide ores are converted into oxide
form before reduction. Non oxide ores can be converted into oxide form
by roasting or calcination.
Roasting :- Roasting is heating of an ore in the presence of oxygen. It
is used to convert suphide ores into oxide form.
Eg :- 2 ZnS + 3O2 2 ZnO + 2SO2
Calcination :- Calcination is heating of an ore in the absence of oxygen.
It is used to convert sulphide ores into oxide form.
Eg :- ZnCO3 ZnO + CO2
The oxide ore is then reduced to the metal by heating with a reducing
agent. The most common reducing agent is coke (carbon).
Eg :- ZnO + C Zn + CO
heat
heat
heat
18.
19. Thermit reactions :-
Sometimes reactive metals like Na, Ca, Al etc. are used
as reducing agents to obtain metals from their oxides.
Mn + 3Al2O3 + Heat
(Manganese)
Eg :- 3MnO2 + 4Al
(Manganese
dioxide)
The reaction between metal oxides and aluminium is
highly exothermic and the metals are obtained in molten
state. Such reactions are called thermit reactions.
The reaction between iron oxide and aluminium
produces molten iron. This reaction is used to join rail
tracks, broken machine parts etc.
Fe2O3 + 2Al Al2O3 + 2Fe + Heat
21. Extraction of metals at the top of the activity series :-
Metals at the top of the activity series like K, Na, Ca, Al etc. cannot
be obtained from their ores by simple heating or by heating with
reducing agents. They are obtained by electrolytic reduction of their
molten chlorides.
Eg :- When electric current is passed through molten sodium
chloride, sodium metal is deposited at the cathode and chlorine gas is
deposited at the anode.
At cathode :- Na + + e - Na (Sodium metal)
At anode :- 2Cl - Cl2 + 2e - (Chlorine gas)
22. Refining of metals :-
The removal of impurities from the metal to obtain the pure metal is
called refining of metals. The most common method for refining of
metals is electrolytic refining.
In this method a block of the impure metal is made the anode and a
thin sheet of the pure metal is made the cathode. The electrolyte is a salt
solution of the metal to be purified.
Eg :- In the electrolytic refining of copper, a block of impure copper is
made the anode and a thin sheet of pure copper is made the cathode.
The electrolyte is acidified copper sulphate solution. When electric
current is passed through the electrolyte, pure copper from the anode is
deposited at the cathode and the impurities settle down as anode mud.
23. Corrosion :-
Corrosion is the damage caused to metals due to the reaction of metals
with oxygen, moisture, carbon dioxide etc.
Eg :- Formation of brown coating of rust over iron.
Formation of green coating of basic copper carbonate over copper.
Formation of black coating of silver sulphide over silver.
To show that air and moisture are necessary for the rusting of iron :-
Take three test tubes marked 1,2,3 and put iron nails in each of them. Put some
anhydrous calcium chloride in test tube 1 to absorb moisture. Pour some boiled distilled
water in test tube 2 and pour some oil over it to prevent air into the test tube. Pour some
water in test tube 3. Cork the test tubes and leave them for a few days. The nails in test
tube 1 does not get rusted because it had only air and no water. The nails in test tube 2
does not rust because it had only water and no air. The nails in test tube 3 gets rusted
because it had air and water.
24. Prevention of corrosion :-
Corrosion of metals can be prevented by :-
i) Applying oil or grease.
ii) Applying paint.
iii) By galvanisation. (Coating with zinc)
iv) By tinning. (Coating with tin)
v) By electroplating. (Coating a less reactive metal like chromium)
vi) By alloying. (Making alloys)
Alloy :-
An alloy is a homogeneous mixture of a metal with other metals or
non metal.
Eg :- Steel – iron, carbon
Stainless steel – iron, carbon, cobalt, nickel
Brass – copper, zinc
Bronze – copper, tin
Solder – Lead, tin (used for welding electrical wires together)
If one of the metals in an alloy is mercury, it is called an amalgam.
