2. Metal Reactivity Series
Metal Symbol Reactivity Extraction
Displaces H2 gas from water, steam and acids and forms hydroxides.
Displaces H2 gas from steam and acids and forms hydroxides.
Carbon C Included for comparison.
Displaces H2 gas from steam and acids and forms hydroxides. Reduction using carbon.
Smelting with coke.
(calcination and roasting)
Displaces H2 gas from acids only and forms hydroxides.
Hydrogen H Included for comparison.
Copper Cu Combines with O2 to form oxides and cannot displace H2.
Heat or physical extraction methods.
Found free in nature, oxides decompose with heating.
Found in native state.
3. EXTRACTION OF METALS: ORES AND MINERALS
• The compounds which contain metals along with impurities are
• Ores are the minerals from which metals can be easily and
• Very few metals such as noble metals, i.e., Gold, Silver, Platinum etc.
Are present in their original metallic forms in nature.
• Metallurgy is the field of science that deals with the extraction of
metals from ores which are naturally found in the environment.
5. EXTRACTION OF METALS: ORES AND MINERALS
• Most of the elements especially metals are present in combination
with other elements or with sand, limestone, and earthy impurities
and these are called minerals.
• An element may combine with a variety of other elements to make
myriad (many) minerals but out of them, only a few are viable
sources of that metal. Such sources are called ores
6. EXTRACTION OF METALS: ORES AND MINERALS
• Smelting is a process of applying heat to ore in order to extract a base
• Calcination is a process where the air or Oxygen might be supplied in
limited quantity, or the ore is heated in the absence of air. Calcination
involves the thermal decomposition of carbonate ores.
• Roasting includes heating of ore at lower than its melting point in the
presence of oxygen or air. Roasting involves the oxidation
(displacement reaction) of sulphide ores.
Concentration of Ore
Metals of high
Metals of medium
Metals of low
Enrichment/ Concentration of Ores
At cathode: Na+ + e– → Na
At anode: 2Cl– → Cl2 + 2e–
High reactive metals are obtained by
electrolytic reduction. For example, sodium,
magnesium and calcium are obtained by the
electrolysis of their molten chlorides and
aluminium is obtained by the electrolytic
reduction of aluminium oxide.
10. Electrolysis of molten Al2O3 (Bauxite)
• Aluminium is mostly extracted from its bauxite ore.
• The ore is mechanically crushed and pulverized.
• Pure aluminium is a silver-white metal with many desirable features.
• Cryolite is a salt of sodium aluminium hexafluoride. It is represented as Na3AlF6.
12. ELECTROLYTIC REFINING OF METALS
Electrolytic refining of copper. The
electrolyte is a solution of acidified
copper sulphate. The anode is impure
copper, whereas, the cathode is a
strip of pure copper. On passing
electric current, pure copper is
deposited on the cathode
13. EXTRACTION OF METALS: ORES AND MINERALS
• The process of extracting metal ores buried deep underground is
called mining. The metal ores are found in the earth’s crust in
varying abundance. The extraction of metals from ores is what
allows us to use the minerals in the ground. The ores are very
different from the finished metals that we see in buildings and
bridges. Ores consist of the desired metal compound and the
impurities and earthly substances called gangue.
14. EXTRACTION OF METALS: ORES AND MINERALS
• The extraction of metals and their isolation occurs over a few major
• Concentration of Ore – Here the ore is separated from earthy
• Isolation of metal from concentrated Ore – Here the ore is converted
to its oxide form and then reduced. The steps involved are either
calcination or roasting and then heating with a reducing agent.
• Purification of the metal – Here the metal is purified for practical
• Silver articles become black after some time when exposed to air. This
is because it reacts with sulphur in the air to form a coating of silver
• Copper reacts with moist carbon dioxide in the air and slowly loses its
shiny brown surface and gains a green coat. This green substance is
basic copper carbonate.
• Iron when exposed to moist air for a long time acquires a coating of a
brown flaky substance called rust.
16. PREVENTION OF CORROSION
The rusting of iron can be prevented by painting, oiling, greasing,
galvanising, chrome plating, anodising or making alloys.
Galvanisation is a method of protecting steel and iron from rusting by
coating them with a thin layer of zinc.
An alloy is a homogeneous mixture of two or more metals, or a metal
and a non-metal. It is prepared by first melting the primary metal, and
then, dissolving the other elements in it in definite proportions. It is
then cooled to room temperature.
The electrical conductivity and melting point of an alloy is less than
that of pure metals.
• Anodising: Anodising is an electrolytic process for producing thick
oxide coatings (layers), usually on aluminium and its alloys to
improve corrosion resistance.
• The process is called anodising because the part to be treated
forms the anode electrode of an electrolytic cell.
• Anodising is the process of using the aluminium as an anode within
an electrolyte bath. When a cathode is positioned within the
anodising tank and a current passed through the medium, the
oxygen reacts with the surface of the aluminium creating an anodic
layer. The longer the aluminium is in these conditions, the thicker
the protective layer.
Anodizing process occurs in
an electrochemical cell, in
which the anode is the
anodized part and the cathode
is a plate/rod made of a
material chemically inert in the
acidic electrolyte (carbon,
stainless steels, nickel).
•Electrochemical reaction at the anode:
6OH-(aq) → 3O2(g) + 6H+ + 6e–
•Oxygen reacts with aluminium anode
to form a thick protection oxide layer.
4Al(s) + 3O2(g) → 2Al2O3(s)
•Aluminium oxide can be dyed.
•Electrolyte may be dil H2SO4,
Chromic acid, Oxalic acid etc.
•Electrochemical reaction at the
6H+(aq) + 6e– → 3H2(g)
• Resulting anodizing reaction
4Al + 6H2O = 2Al2O3 + 6H2
• Cathode may be of Al, C, Pb, Au
Aluminum, Aluminum alloys, Magnesium, Titanium, Niobium,
Nickel, Copper, Zinc, Stainless Steel etc can be anodized.
• Electroplating or Plating is a
process of depositing a thin
coating of metal on a
• Coating of gold on
• Coating of chromium on iron
• Coating of zinc/copper on
• Electroplating, also known as electrochemical deposition or
electrodeposition, is a process for producing a metal coating on a
solid substrate through the reduction of cations of that metal by
means of a direct electric current. The part to be coated acts as the
cathode (negative electrode) of an electrolytic cell; the electrolyte is
a solution of a salt of the metal to be coated; and the anode (positive
electrode) is usually either a block of that metal. The current is
provided by an external power supply.
• Galvanisation or galvanization or galvanizing is the process of applying a
protective zinc coating (plating) to iron or steel, to prevent rusting.
The protection is two fold-
• Physical protection from Moisture and air.
• Electrochemical cathode protection.
• Electro-galvanizing Provides thin coating with
strong bonding and better finish.
• Hot dip galvanizing is most common method, in
which steel sections are submerged in a bath of