Carbon And Its Compounds PDF

CARBON AND ITS COMPOUNDS Why is it difficult for carbon to gain or lose 4 electrons? The atomic number of carbon is 6. Its electronic configuration is 2,4. It requires 4 electrons to achieve the inert gas electronic configuration, but carbon cannot form an ionic bond. It could gain 4 electrons formi...

CARBON AND ITS COMPOUNDS Why is it difficult for carbon to gain or lose 4 electrons? The atomic number of carbon is 6. Its electronic configuration is 2,4. It requires 4 electrons to achieve the inert gas electronic configuration, but carbon cannot form an ionic bond. It could gain 4 electrons forming C4- anion. But it would be difficult for the nucleus with 6 protons to hold on to 10 electrons (ie,4 extra electrons). It could lose 4 electrons forming C4+ cation, but it requires a large amount of energy to remove 4 electrons. Thus, carbon overcomes this problem by sharing of its valence electrons with other carbon atoms or with atoms of other elements. Define covalent bond. A covalent bond is a type of chemical bond that forms between two atoms by sharing one or more pairs of electrons. Covalent bond takes place between non-metals. Covalent compounds are the compounds which are formed by sharing of electrons between two atoms. Types of covalent bonds Depending on the number of electron pairs, the covalent bond is divided into three types. 1.Single Covalent Bond A single covalent bond is a type of chemical bond that forms between two atoms by sharing one pair of electrons. This bond is denoted by a −. Eg) i) Hydrogen(H2) molecule In the case of hydrogen (H), a single covalent bond is formed when two hydrogen atoms share one electron pair. H2 → diatomic molecule Atomic no: (Z) : 1 Electronic Configuration: 1 1  Single covalent bond (1 pair of e-): H2 Molecule, denoted by H−H ii) Chlorine (Cl2) molecule Z: 17, E.C: 2, 8, 7 denoted by Cl−Cl iii) Sulphur molecule (S8) : Ring structure Z: 16, E.C: 2,8,6 2 iv) Water (H2O) Hydrogen Oxygen Z: 1, E.C: 1 Z: 8, E.C: 2,6 denoted by, H−O−H v) Ammonia (NH3) Nitrogen Hydrogen Z: 7, E.C: 2,5 Z: 1, E.C: 1 denoted by, H−N−H H vi) Methane (CH4) Carbon Hydrogen Z: 6, E.C: 2,4 Z: 1, E.C: 1 denoted by, 3 2. Double Covalent Bond A double covalent bond is a type of chemical bond that forms between two atoms by sharing two pairs of electrons. The double bond is represented as =. i) Oxygen (O2) molecule Z: 8, E.C: 2, 6 O≡O ii) Carbon dioxide (CO2) Carbon Oxygen Z: 6, E.C: 2,4 Z: 8, E.C: 2,6 O=C=O 3.Triple Covalent Bond A triple covalent bond is a type of chemical bond that forms between two atoms by sharing three pairs of electrons. Such bonds are written as ≡. i) Nitrogen (N2) molecule Z: 7, E.C: 2, 5 N≡N 4 Ii) Ethyne (C2H2) Carbon Hydrogen Z: 6, E.C: 2,4 Z: 1, E.C: 1 H −C≡C−H Difference between ionic and covalent compounds Property Ionic Compounds Covalent Compounds Compound Formation Formed by the transfer Formed by the sharing of of electrons between electrons between atoms. atoms. State Generally exist in the Can exist in solid, liquid solid state. or gaseous states. Melting and Boiling Have high melting and Have low melting and Points boiling points. boiling points. Solubility Soluble in water (polar Mostly insoluble in water solvent). but soluble in organic solvents. Electricity Conduction Conduct electricity in Do not conduct electricity molten state and in molten state or aqueous solution. aqueous solution Allotropes of carbon Allotropy: The phenomenon in which the element exists in two or more different physical states with similar chemical properties is called allotropy. Carbon has three main Allotropes Diamond: In this, each carbon atom is bonded to four other atoms of carbon forming rigid three-dimensional structures. It is the hardest substance. Graphite: In this, each carbon atom is bonded to three other carbon atoms giving hexagonal array. One of these bonds is a 5  double bond. It is smooth and slippery. It is a good conductor of electricity. Buckminster Fullerene: Identified as C−60, which has carbon atoms arranged in the shape of a football. Textbook Q & A (page no: 61) 1. What would be the electron dot structure of carbon dioxide which has the formula CO2? Ans: Done above (refer page: 4) 2. What would be the electron dot structure of a molecule of Sulphur which is made up of eight atoms of Sulphur? (Hint – The eight atoms of Sulphur are joined together in the form of a ring). Ans. Done above (refer page: 2) ************* Versatile Nature of Carbon The existence of such a large number of organic compounds is due to the following nature of carbon: - Catenation Tetravalency Catenation: Carbon has the unique ability to form bonds with other atoms of carbon giving rise to large molecules. This property is called catenation. Carbon atoms forms compounds with different types of arrangements such as long chains, branched chain and cyclic chain structures (ring compounds). 6  Carbon atoms may be linked by single, double, or triple bonds. Compounds of carbon which are linked by only single bonds between the carbon atoms are called saturated compounds. Compounds of carbon which are linked by double bonds and triple bonds between the carbon atoms are called unsaturated compounds. Tetravalency: Carbon has valency 4. It is capable of bonding with 4 other atoms of carbon or atoms of some other monovalent element. Compounds of carbon are formed with oxygen, hydrogen, nitrogen, sulfur, chlorine, and many other elements giving rise to compounds with specific properties which depend on the elements other than carbon present in the molecule. Note: Bonds that carbon forms with most other elements are very strong, making this compound exceptionally stable. One reason for formation of the strong bonds by carbon is its small size. This enables the nucleus to hold on to the shared pair of electrons strongly. Saturated & Unsaturated carbon compounds Saturated compounds (Carbon atoms linked together with a single bond):- Electron dot structure: Examples Eg: Ethane (C2H6) 7 Propane (C3H8) Unsaturated compounds (Carbon atoms linked together with double or triple bonds):- Electron dot structure: Eg: Ethene (C2H4) Ethyne (C2H2) Note: Saturated compounds are more stable than unsaturated compounds and they are less reactive under normal conditions. Compounds of carbon having double or triple bonds between the carbon atoms are known as unsaturated carbon compounds and they are more reactive than the saturated carbon compounds. 8  Hydrocarbons Compounds formed by carbon and hydrogen. Hydrocarbons ___________________________________________ Saturated hydrocarbons Unsaturated hydrocarbons ________________ Alkanes ( − ) Alkenes ( = ) Alkynes ( ≡ ) Naming: No: of carbon Word root (Base name) 1 Meth- 2 Eth- 3 Prop- 4 But- 5 Pent- 6 Hex- 7 Hept- 8 Oct- 9 Non- 10 Dec- 9  Saturated hydrocarbons Alkanes Saturated (single bonded) hydrocarbons are called Alkanes. Its name ends with ‘ane’. The general formula of alkane is CnH2n+2 , where ‘n’ is the no: of carbon atoms. Formulae and structures of Alkanes No: of Name Molecular Structural formula Consolidated structure C- formula atoms 1 Methane CH4 CH4 2 Ethane C2H6 CH3−CH3 3 Propane C3H8 CH3−CH2− CH3 4 Butane C4H10 CH3−CH2−CH2− CH3 5 Pentane C5H12 CH3−CH2−CH2−CH2− CH3 6 Hexane C6H14 CH3−CH2−CH2−CH2−CH2− CH3 10  Unsaturated hydrocarbons Alkenes Unsaturated hydrocarbons with a double bond are called Alkenes. Its name ends with ‘ene’. The general formula of alkane is CnH2n, where ‘n’ is the no: of carbon atoms. Formulae and structures of Alkenes No: of Name Molecular Structural formula Consolidated structure C- formula atoms 2 Ethene C2H4 CH2=CH2 3 Propene C3H6 CH2=CH− CH3 4 Butene C4H8 CH2=CH−CH2− CH3 5 Pentene C5H10 CH2=CH−CH2−CH2− CH3 6 Hexene C6H12 CH2=CH−CH2−CH2−CH2− CH3 11  Unsaturated hydrocarbons Alkynes Unsaturated hydrocarbons with a triple bond are called Alkynes. Its name ends with ‘yne’. The general formula of alkane is CnH2n-2, where ‘n’ is the no: of carbon atoms. Formulae and structures of Alkenes No: of Name Molecular Structural formula Consolidated structure C- formula atoms 2 Ethyne C2H2 CH≡CH 3 Propyne C3H4 CH≡C− CH3 4 Butyne C4H6 CH≡C−CH2− CH3 5 Pentyne C5H8 CH≡C−CH2−CH2− CH3 6 Hexyne C6H10 CH≡C−CH2−CH2−CH2− CH3 *Practice the electron dot structures of all Alkanes, Alkenes and Alkynes (eg: As shown on page7 & 8). 12