Revision Notes for Board Exams | Metals and Non-Metals

Metals and Non- Metals  is one of those chapters which can fetch you lot of marks, if you’ve prepared well for it! We have prepared for you a simplified version of this very important chapter.

• Elements can be classified as metals and non-metals on the basis of their properties.

• Example of some metals are :
Iron (Fe), Aluminium (Al), Silver (Ag), Copper (Cu)
• Examples of some non-metals are :
Hydrogen (H), Nitrogen (N), Sulphur (S), Oxygen (O)

ALSO SEE HINDI VERSION OF THIS CHAPTER 

धातु एवं अधातु

II. CHEMICAL PROPERTIES OF METALS

(A)Reaction with Air :
Metals combine with oxygen to form metal oxide.
Metal + O2  —> Metal oxide
Examples :
(i) 2Cu + O2  —> 2CuO  Copper oxide (black)
(ii) 4Al + 3O2  —> 2Al2O3  Aluminium oxide
(iii) 2Mg + O2 —>  2MgO
Different metals show different reactivities towards O2

• Na and K react so vigorously that they catch fire if kept in open so they are kept
immersed in kerosene.
• Surfaces of Mg, Al, Zn, Pb are covered with a thin layer of oxide which prevent
them from further oxidation.
• Fe does not burn on heating but iron fillings burn vigorously.
• Cu does not burn but is coated with black copper oxide.                                                                                                                                               • Au and Ag does not react with oxygen.

 

 

Amphoteric Oxides : Metal oxides which react with both acids as well as bases to
produce salts and water are called amphoteric oxides.
Examples :

Al2O3+ 6HCl —> 2AlCl3+ H2O

Al2O3+ 2NaOH —> 2NaAlO2+ H2O   Sodium Aluminate

(B) Reaction of Metals with Water :
Metal + Water —> Metal oxide + Hydrogen
Metal oxide + Water —> Metal hydroxide

Examples :
(i) 2Na + 2H2O 2NaOH + H2+ Heat

(ii) Ca + 2H2O Ca(OH) 2 + H2

(iii)Mg + 2H2O Mg(OH)2+ H2

(iv) 2Al + 3H2O Al2O3+ 3H2

(v) 3Fe + 4H2O Fe3O4+ 4H2

(C)Reaction of Metals with Acids (Dilute) :
Metal + Dilute acid Salt + H2
Cu, Ag, Hg do not react with dil. acids.
Examples :
(i) Fe + 2HCl FeCl2+ H2
(ii) Mg + 2HCl MgCl2+ H2
(iii)Zn + 2HCl ZnCl2+ H2
(iv) 2Al + 6HCl 2AlCl3+ 3H2

(D)Reaction of Metals with Solutions of other Metal Salts :
Metal A + Salt solution B Salt solution A + Metal B
• Reactive metals can displace less reactive metals from their compounds in solution
form.

Fe + CuSO4 FeSO4+ Cu

 

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REACTIVITY SERIES

The reactivity series is a list of metals arranged in the order of their decreasing activities.

Reaction of Metals with Non-metals
• Reactivity of elements is the tendency to attain a completely filled valence shell.
• Atoms of the metals lose electrons from their valence shell to form cation. Atom of
the non-metals gain electrons in the valence shell to form anion.
E.g., Formation of NaCl

Ionic Compounds

The compounds formed by the transfer of electrons from a metal to a non-metal are
called ionic compounds or electrovalent compounds.
Properties of Ionic Compounds
1. Physical nature : The are solid and hard, generally brittle.
2. Melting and Boiling Point : They have high melting and boiling point.
3. Solubility : Generally soluble in water and insoluble in solvents such as kerosene,
petrol etc.
4. Conduction of electricity : Ionic compounds conduct electricity in molten and
solution form but not in solid state.

 

Sample Paper Class 10 Board Exam – Science

 

Occurrence of Metals

Minerals : The elements or compounds which occur naturally in the earth’s crust are
called minerals.
Ores : Minerals that contain very high percentage of particular metal and the metal
can be profitably extracted from it, such minerals are called ores.

Extraction of Metals from Ores
Step 1. Enrichment of ores.
Step 2. Extraction of metals.
Step 3. Refining of metals.

 

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Steps Involved in Extraction of Metals from Ores

Some Important Terms
(a) Gangue : Ores are usually contaminated with large amount of impurities such as soil,
sand etc. called gangue.
(b) Roasting : The sulphide ores are converted into oxides by heating strongly in the presence of excess air. This process is called roasting.

(c) Calcination : The carbonate ores are changed into oxides by heating strongly in limited
air. This process is called calcination.

(d) Reduction : Metal oxides are reduced to corresponding metals by using reducing agent
like carbon.

Refining of Metals
The most widely used method for refining impure metal is electrolytic refining.

• Anode : Impure copper
• Cathode : Strip of pure copper
• Electrolyte : Solution of acidified copper sulphate
(a) Onpassingthecurrentthroughelectrolyte,theimpuremetalfromanodedissolvesinto
the electrolyte.
(b) An equivalent amount of pure metal from the electrolyte is deposited at the cathode.
(c) The insoluble impurities settle down at the bottom of the anode and is called anode
mud.
Corrosion
The surface of some metals such as iron is corroded when they are exposed to moist air for a long period of time. This is called corrosion.
(i) Silver becomes black when exposed to air as it reacts with air to form a coating of
silver sulphide.
(ii) Copper reacts with moist carbon dioxide in the air and gains a green coat of copper
carbonate.
(iii) Iron when exposed to moist air acquires a coating of a brown flaky substance called
rust.
Prevention of Corrosion
The rusting of iron can be prevented by painting, oiling, greasing, galvanizing, chrome
plating, anodizing or making alloys.

 

Galvanization : It is a method of protecting steel and iron from rusting by coating them
with a thin layer of zinc.

Alloy : An alloy is a homogenous mixture of two or more metals or a metal and a non-
metal.

Iron : Mixed with small amount of carbon becomes hard and strong.
Steel : Iron + Nickel and chromium
Brass : Copper + Zinc
Bronze : Copper + Tin (Sn)
Solder : Lead + tin
Amalgam : If one of the metal is mercury (Hg).

 

ALSO SEE 

Carbon and it’s Compounds

 

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