Carbon and its compounds class 10 notes | cbse24

Carbon is an element. The symbol of carbon is C.It is non-metal. The name carbon is derived from the Latin word 'carbo' which means 'coal'.This is because carbon is the main constituent of coal. 

The amount of carbon present in the crust and atmosphere is very small. For example, the earth contains only 0.02% carbon in the form of minerals(like carbonates, coal and petroleum etc) and the atmosphere has only 0.03% of carbon dioxide gas. All living things, plants and animals are made up of carbon-based compounds which are called organic compounds.

An important point about carbon

1:-Carbon always forms covalent bonds

The atomic number of carbon is 6 which means that a neutral atom of carbon has 6 electrons. So, the electronic configuration of carbon is 2,4. It is clear that carbon has 4 electrons in the outermost shell. So carbon atoms can achieve the inert gas electrons arrangement only by the sharing of electrons, therefore, carbon always forms covalent bonds.

2:-Carbons is Tetravalent

A carbon atom has 4 electrons in its outermost shell, so it required 4 more electrons to achieve the stable,8-electron inert gas arrangement. Since one carbon atom requires 4 electrons to achieve the eight-electron inert gas structure, therefore the valency of carbon is 4.

3:-Self combination

The most outstanding property of carbon is its ability to combine with itself, atom to atom long chains.Example:-octane(C8H18) one of the constituents of petrol has a chain of 8 carbon atoms.

Occurrence of Carbon

Carbon occurs in nature in the 'free state'(as elements) as well as in the 'combined state'(in the form of compounds with other elements)

1:-In free state:-Carbon occurs in nature in the forms: of diamond and graphite and buckminsterfullerene(C60).

2:-In the combined state:-Carbons occurs in nature in the form of compounds such as (i) Carbon dioxide gas in air (ii)Carbonates(like limestone, marble and chalk)

Allotropes of Carbon

The various physical forms in which an element can exist are called allotropes of the element. The carbon element exists in three solid forms called allotropes.

  (i) Diamond

  (ii) Graphite

  (iii) Buckminsterfullerene

Organic Compounds

The compounds of carbons are known as organic compounds. Apart from carbons, most organic compounds contain hydrogen and many organic compounds contain oxygen or other elements.

Some the examples of organic compounds are:

Types of organic compounds

Some of the common types of organic compounds are:

1:-Hydrocarbons                2:-Haloalkanes(Halogenated hydrocarbons)

3:-Alcohols                        4:-Aldehydes

5:-Ketones                         6:- Carboxylic acids

Hydrocarbons

A compound made up of hydrogen and carbon only is called hydrocarbon (Hydrogen+Carbon=Hydrocarbon). The most important natural source of hydrocarbons is petroleum(or crude oil).

Types of Hydrocarbons

 1:- Saturated Hydrocarbons (Alkanes 'ane')

A hydrocarbon in which the carbon atoms are connected by only single bonds is called a saturated hydrocarbon. An alkane is a hydrocarbon in which the carbon atoms are connected by only single covalent bonds.

The names and molecular formulae of the first five saturated hydrocarbons or alkanes are given below.

The ethane molecule is made up of 2 carbon atoms and 6 hydrogen atoms.The structure of ethane molecule is show in figure.

2:-Unsaturated Hydrocarbons(Alkenes 'ene')

An unsaturated hydrocarbon in which the two carbon atoms are connected by a double bond is called an alkene.

The general formula of an alkene is CnH2n  where n is the number of carbon atoms in its one molecule.

Note:-In Alkene starts from n=2 because if we start from n=1 than CH2 which has no double bond .

3:-Unsaturated Hydrocarbons(Alkyne 'yne')

Ab unsaturated hydrocarbon in which the two carbon atoms are connected by a triple bond is called an alkyne.

The general formula of alkynes is CnH2n-2 where n is the number of carbon atoms in one molecule of the alkyne.

Note:-In Alkynes we take carbon number  n=2 means start from Ethyne not from methyne because if we put n=1 in formula it becomes zero.

4:-Alkyl Groups('yl')

The group formed by the removal of one hydrogen atom from an alkane molecule is called an alkyl group.

The general formula of an alkyl group is CnH2n-1

H