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Carbon and its compounds notes

CLASS -10

CHAPTER- 4

CARBON AND ITS COMPOUNDS

# What do we know about carbon?

– Carbon is a versatile element.

Food, clothes, medicines, books, or many of the things, all based on the versatile carbon. All living structures are carbon based.

– The earth’s crust has only 0.02% carbon in the form of minerals (like carbonates, hydrogen-carbonates and petroleum) and the atmosphere has 0.03% of carbon di-oxide.

# Basics:-

– Carbon is a chemical element with the symbol C.

– Atomic number- 6, – Mass number-12

– Electronic configuration – 2, 4

 – Outmost shell’s elections – 4 (Tetra valency)

• Group no – 14  

          •         Period no – 2

          •         Bond – Covalent Bond

          •         Carbon is a poor conductor of electricity.  Exception – Graphite.

• Most of carbon compounds’ melting points and boiling points are low.

Covalent Bond –

The atomic no. of carbon is 6 and electronic configuration of carbon is 2,4. It has four electrons in its outermost shell and needs to gain or lose four electrons to attain a noble gas configuration. If it were to gain or lose electrons-

(i) It could gain four electrons forming C4 – anio. But it would be difficult for the nucleus with six protons to hold on to ten electrons. i.e. four extra electrons.

(ii) It could lose four electrons forming C4+ cation. But it would require a large amount of energy to remove four electrons leaving behind a carbon cation with six protons in its nucleus holding on to just two electrons.

Carbon overcomes this problem by sharing its valence electrons with other atoms of carbon or with atoms of other elements. This bond which is made by sharing electrons with the same or other elements is called a covalent bond.

Atoms of other elements like hydrogen, oxygen, nitrogen, and chlorine also show the sharing of valence electrons.

This type of bonding has three types-                                                                                  

(i) single covalent bond

(ii)  Double covalent bond

(iii) Triple covalent bond

1. Single bond- One electron is shared by each atom giving rise to one shared pair of electrons.

1. Hydrogen atomic one no -1

Hydrogen atom

H2 molecules

H – H covalent bond (The single bond between two hydrogen atoms)

H2 -That’s why hydrogen a diatomic molecule.

2. Chlorine (Cl)

Atomic No -17                                                                                                                          

electronic configuration- 2, 8, 7

Outermost shell electrons -7

Electron-dot structure of [Cl2]                                                                                                                                                                         [[[7 electrons in the outermost shell]9

(CI – CI)Cl2   (diatomic molecules) – Single bond between two chlorine atoms

Double bond –

Two electrons contributed by each atom give rise to two shared pairs of electrons. This is said to constitute a double bond between two atoms.

Example – Oxygen molecule, carbon dioxide molecule

Oxygen atoms – (O)-  atomic no. – 8

Electronic configuration (2 ,6)

Outermost shell – 6 electrons

O=O

[Double bond by sharing two pairs of electrons]  (O2 molecule)

Double bond between two Oxygen atoms.

(3) Triple Bond –

Three electrons contributed by each atom give rise to three shared pairs of electrons. (6 electrons in total). This is said to be a triple bond between two atoms.

Example – Nitrogen molecule.

Nitrogen atoms (N)- atomic No -7

Electronic configuration ( 2 ,5 )

Outermost shell – 5 electrons

(Triple bond by sharing three pairs of electrons)

             N2 molecule

The triple bond between two Nitrogen atoms

Electron-dot structure of Methane

[CH4]

Carbon outmost elections – 4

Hydrogen outermost electrons – 1

Electron dot structure of Methane

# Properties of covalent bonds

1. Covalently bonded molecules have low melting points and low boiling points.                           

2. They have weak intermolecular forces.

3. They are most cases poor conductor of electricity because it does not have charged particles.

Covalent bond vs Ionic bond

Covalent bondsIconic bonds  
1. Melting points and                                                     boiling points are low.Melting points and                                                       boiling points are high.
2. The force of attraction between molecules is weak.Force of attraction                                                                   between molecules is high.
3. Generally poor conductor of electricity.3. Good conductor of electricity.

# Versatile nature of Carbon –

Two main factors enable carbon to form a large no of compounds.

(i) Catenation

(ii) Tetra Valency

(i) Catenation- Carbon has the unique ability to form bonds with other atoms of carbon, giving rise to large molecules. This property is called catenation.

Carton can concate by long chains, branched atoms of carbon or in ring forms.

[ – C- C – C – C – C – ] Chain form                   

Branched form

Ring form

  • Silicon also forms compounds with hydrogen which have chains of up to seven or eight atoms, but these compounds are very reactive.
  • Carbon-carbon bond is very strong and hence stable.

(ii) Tetra Valency –

Carbon has a valency of four, it has the capability of bonding with four other atoms of carbon or atoms of some other mono-valent element.

Note – The reason of strong bonds by carbon is its small size. This enables the nucleus to hold on to the shared pairs of electrons strongly, bonds formed by elements of larger atoms are much weaker.

# Saturated and unsaturated carbon compounds :   Saturated carbon compounds – Carbon compounds which are having single bond between the carbon atoms are known as saturated carbon compounds. Example – ethane [C2H6) , propane ( C3 H8 ) Electron-dot structure of ethane

( single bond )

[ C2H6 , Ethane]

Electron-dot structure of Propane –

(single bond)

[C3H8 Propane]

                                                

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