CLASS 10 SCIENCE CARBON AND ITS COMPOUNDS NCERT IMPORTANT SHORT NOTES

Carbon :- Important points

• Carbon is an element.
• The symbol of carbon is “C”.
• The word carbon is derived from the latin word “carbo” which means coal.
• Atomic noumber of carbon is 6.
• Electronic Configuration :- 2, 4
• Number of electrons in Outermost shell :- 4
• Valency of carbon :- 4
• Atomic mass number of carbon is 12.
• Carbon is a non metal.
• In earth crust there is only 0.02% of carbon is in mineral form. For eg. Carbonates, coal and petroleum etc.
• In atmosphere there is only 0.03 % of carbon is present, which is in the form of carbon dioxide gas.
• All the living things (plants & animals) are made up of carbon based compounds.

• Carbon acquire inert gas configuration or stability by sharing of electrons.
• Carbon always forms covalent bonds.

How to test a material for presence of carbon content in it ?

We can test the presence of carbon in a material on the basis of fact that carbon and its compounds burn in air to give carbon dioxide gas which turns lime (CaO) water milky.

Experiment Test : For presence of carbon in a given material.

1). Burn the given material in air.
2). Pass the exhaust gas formed, through the lime water (CaO).
3).If the lime water turns milky, then the  given material contains carbon.

Why carbon is teravalent ?

• 1). A carbon atom requires four electrons to achieve inert gas configuration.
• 2). Valency of carbon is 4.
• 3). Therefore, carbon is tetravalent.

Self combination property of carbon:

• The formation of strong bonds by carbon atoms among themselves and with other elements, makes the carbon compounds exceptionally stable.
• The property of self combination  is known as catenation.

Occurence of carbon:

In nature, carbon occurs in two states,

• Free state
• Combined state

Allotropes or allotropy

Allotropy or allotropism is the property of some chemical elements to exist in two or more different forms, in the same physical state, known as allotropes of the elements.

Allotropes are different structural modifications of an element: the atoms of the element are bonded together in a different manner.

Allotropes of carbon

• The physical forms in which an element can exist are called allotropes.
• Three allotropes of carebon are,
• Diamond
• Graphite
• Buckminster Fullerene

Properties of diamond :

• Made up of  pure carbon only.
• Visibly diamond is colourless transparent substance.
• Physically quite heavy and hard.
• Hardest natural substance.
• Does not conduct electricity.
• Have extra ordinary brilliance.

Structure of diamond

• Diamond is a solid form of the element carbon with its atoms arranged in a crystal structure called diamond cubic.
• Each carbon in diamond crystal is linked to four other carbon atoms by strong covalent bond.
• Diamond crystal has a tetrahedral arrangement of carbon atoms i.e the four surrounding carbon atoms are at the four vertices of a regular tetrahedron.
• 3D arrangement of carbon atoms in a tetrahedral structure gives high density to the diamond crystal.
• Diamond crystal do not conduct electricity because of no free  electrons.

Uses of Diamond

• Uses of diamond in jewellery.
• Uses of diamond in industry for making cutting , grinding, drilling & polisting tools.
• For production of surgical tools.
• In cosmetics and beauty products.
• Diamonds are also used in audio or DJ equipments.

Properties of graphite :

• Graphite is made up of carbon.
• Visually, it is greyish black opaque.
• It is lighter and less denser than diamond.
• It conducts electricity.
• On heating, graphite burns and forms carbon dioxide.

Structure of graphite :

• Graphite has a layered structure that consists of rings of six carbon atoms arranged in widely spaced horizontal sheets.
• Graphite is formed by the metamorphosis of sediments containing carbonaceous material.
• The various layer of carbon atom in graphite are held by weak vander waal forces.
• Each carbon atom in graphite layer is joined to other three carbon atoms by strong covalent bonds to form flat hexagonal rings.
• Graphite conducts electricity due to presence of free electrons .

Uses of graphite :

• Graphite is used in
• pencils,
• lubricants,
• crucibles,
• foundry facings,
• polishes,
• arc lamps,
• Electrodes in batteries,
• brushes for electric motors,
• cores of nuclear reactors.

Buckminster Fullerene

An allotrope of carbon containing cluster of 60 carbon atoms joined together to form spherical molecule.

• Buckminster fullerene is a type of fullerene with the formula C₆₀.
• It has a cage-like fused-ring structure made of twenty hexagons and twelve pentagons.
• It resembles a soccer ball.
• It is insoluble in water.
• It a dark solid at room temperature.