Carbon and its Compounds Class 10 Notes Science Chapter 4

Carbon and its Compounds Notes CBSE Class 10 Science Chapter 4

Bonding in Carbon: The Covalent bond, Electron dot structure, Physical properties of organic compounds, Allotropes of Carbon.

Covalent Bond: 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 four electrons forming C4- cation. But it would be difficult for the nucleus with six protons to hold on to ten electrons.

It could lose four electrons forming C4+ cations. But it requires a large amount of energy to remove four electrons.

Thus, carbon overcomes this problem by sharing of its valence electrons with other carbon atoms or with atoms of other elements.

The bond formed by mutual sharing of electron pairs between two atoms in a molecule is known as Covalent Bond.

Types of Covalent Bond:

  • Single Covalent Bond: When a single pair of electrons are shared between two atoms in a molecule. For example; F2, Cl2, H2 etc.
  • Double Covalent Bond: When two pairs of electrons are shared between two atoms in a molecule. For example; O2, CO2 etc.
  • Triple Covalent Bond: When three pairs of electrons are shared between two atoms in a molecule. For example; N2 etc.
  • Electron Dot Structure: The electron dot structures provides a picture of bonding in molecules in terms of the shared pairs of electrons and octet rule.Formation of Hydrogen Molecule
    Atomic number of Hydrogen = 1
    Number of valence electrons = 1
    Carbon and its Compounds Class 10 Notes Science Chapter 4 1
  • Formation of CH4 Molecule
    Atomic number of Carbon = 6 [2, 4]
    Number of valence electrons = 4
    Atomic number of Hydrogen = 1
    Number of valence electrons = 1
    Carbon and its Compounds Class 10 Notes Science Chapter 4 2Formation of CO2 Molecule
    Atomic number of Carbon = 6 [2, 4]
    Number of valence electrons = 4
    Atomic number of Oxygen = 8 [2, 6]
    Number of valence electrons = 6
    Carbon and its Compounds Class 10 Notes Science Chapter 4 3Formation of H2S Molecule
    Atomic number of Sulphur = 16 [2, 8, 6]
    Number of valence electrons = 6
    Carbon and its Compounds Class 10 Notes Science Chapter 4 4
    Physical Properties of Organic Compounds
    Most of the organic compounds have low boiling and melting point, due to the weak force of attraction (i.e., the inter-molecular force of attraction) between these molecules.
    Most carbon compounds are poor conductors of electricity, due to the absence of free electrons and free ions.

    Compounds M.P. (K) B.P. (K)
    Acetic acid (CH3COOH) 290 391
    Chloroform (CHCl3) 209 334
    Ethanol (CH3CH2OH) 156 351
    Methane (CH4) 90 111

    Allotropes of Carbon
    Allotropy: The phenomenon in which the element exists in two or more different physical states with similar chemical properties are called Allotropy.

    Carbon has Three Main Allotropes

    • Diamond: In this, carbon, an atom is bonded to four other atoms of carbon forming three-dimensional structures. It is the hardest substance and an insulator. It is used for drilling rocks and cutting. It is also used for making jewellery.
    • Graphite: In this, each carbon atom is bonded to three other carbon atoms. It is a good conductor of electricity and used as a lubricant.
    • Buckminster Fullerene: It is an allotrope of the carbon-containing cluster of 60 carbon atoms joined together to form spherical molecules. It is dark solid at room temperature.

    Versatile nature of Carbon, Hydrocarbons, Isomerism, Homologous series, Functional groups, Nomenclature of functional groups.

    Versatile Nature of Carbon: The existence of such a large number of organic compounds is due to the following nature of carbon,

    • Catenation
    • Tetravalent nature.

    (i) Catenation: The self linking property of an element mainly carbon atom through covalent bonds to form long straight, branched and rings of different sizes are called Catenation.
    This property is due to

    • The small size of the carbon atom.
    • The great strength of the carbon-carbon bond.

    Carbon can also form stable multiple bonds (double or triple) with itself and with the atoms of other elements.
    Straight Chain
    Carbon and its Compounds Class 10 Notes Science Chapter 4 5
    Branched Chain
    Carbon and its Compounds Class 10 Notes Science Chapter 4 6
    Rings
    Carbon and its Compounds Class 10 Notes Science Chapter 4 7

    (ii) Tetravalent Nature: Carbon has valency of four. It is capable of bonding with four other atoms of carbon or some other heteroatoms with single covalent bond as well as double or triple bond.
    Carbon and its Compounds Class 10 Notes Science Chapter 4 8

    Hydrocarbons: Compounds of carbon and hydrogen are known as hydrocarbons.
    For example; Methane (CH4), Ethane (C2H6), Ethene (C2H4), Ethyne (C2H2) etc.
    Carbon and its Compounds Class 10 Notes Science Chapter 4 9

    Saturated Hydrocarbon (Alkanes): General formula is CnH2n+2.
    n = number of carbon atoms.
    In this, the carbon atoms are connected by only a single bond.
    For example; Methane (CH4), Ethane (C2H6) etc.
    Carbon and its Compounds Class 10 Notes Science Chapter 4 10

    Unsaturated Hydrocarbons
    Alkenes: General formula is CnH2n, where n = number of carbon atoms.
    In this, the two carbon atoms are connected by double bond.
    Carbon and its Compounds Class 10 Notes Science Chapter 4 11

    Alkynes: General formula is CnH2n-2, where n = number of carbon atoms. In this, the two carbon atoms are connected by triple bond.
    Carbon and its Compounds Class 10 Notes Science Chapter 4 12

    Electron Dot Structure of Hydrocarbons
    Carbon and its Compounds Class 10 Notes Science Chapter 4 13

    Isomerism: Compounds having the same molecular formula but different structural formula and properties are known as Isomers and this phenomenon is known as Isomerism.

    Structural Isomerism: Compounds having the same molecular formula but different structures are called Structural isomers. Example: Isomers of butane (C4H10)
    Carbon and its Compounds Class 10 Notes Science Chapter 4 14
    Carbon and its Compounds Class 10 Notes Science Chapter 4 15

    Homologous Series: Series of organic compounds having the same functional group and chemical properties and successive members differ by a CH2 unit or 14 mass units are known as Homologous series.

    Homologous series of Alkanes, Alkenes and Alkynes
    Carbon and its Compounds Class 10 Notes Science Chapter 4 16

    Characteristic of Homologous Series

    • The successive members in homologous series differ by CH2 unit or 14 mass unit.
    • Members of given homologous series have the same functional group.
    • All the members of homologous series shows similar chemical properties.

    Functional Group: An atom or group of atoms present in a molecule which largely determines its chemical properties are called Functional Group.
    Carbon and its Compounds Class 10 Notes Science Chapter 4 17
    Carbon and its Compounds Class 10 Notes Science Chapter 4 18

    Nomenclature of Organic Compounds: It is difficult to remember millions of compounds by their individual common name. Thus, to systematize the nomenclature of organic compounds IUPAC (International Union of Pure and Applied Chemistry) has given certain rule which is as follows:
    1. Identify the Number of Carbon Atoms in the Compound

    S. No Number of Carbon Atoms Word Root (-) (Suffix) Single bond
    1. One carbon atoms (1-C) Meth + ane
    2. Two carbon atoms (2-C) Eth + ane
    3. Three carbon atoms (3-C) Prop + ane
    4. Four carbon atoms (4-C) But + ane
    5. Five carbon atoms (5-C) Pent + ane
    6. Six carbon atoms (6-C) Hex + ane

    2. Identify the functional group

    S. No. Functional Group Prefix Suffix
    1. Double bond (=) ene
    2. Triple bond (≡) yne
    3. Chlorine (—Cl) Chloro
    4. Bromine (—Br) Bromo
    5. Alcohol (-OH) ol
    6. Aldehyde (-CHO) al
    7. Ketone (-CO-) one
    8. Carboxylic acid (-COOH) oic acid

    3. Name the Compounds By Following Order
    Prefix + Word Root + Suffix
    Carbon and its Compounds Class 10 Notes Science Chapter 4 19
    Carbon and its Compounds Class 10 Notes Science Chapter 4 20

    Chemical Properties of Carbon Compounds: The important chemical properties are as follows:
    1. Combustion: The complete combustion of carbon compounds in the air gives carbon dioxide water, heat and light.
    CH3CH2OH(l) + O2(g) → CO2(g) + H2O(l) + Heat and light

    Carbon burns in air or oxygen to give carbon dioxide and heat and light.
    C(s) + O2(g) → CO2(g) + Heat and light

    Saturated hydrocarbons burn with a blue flame in the presence of a sufficient supply of air or oxygen.
    CH4(g) + 2O2(g) → CO2(g) + 2H2O(l) + Heat and light

    In presence of limited supply of air, saturated hydrocarbon forms a sooty flame.

    Unsaturated hydrocarbons burn with a yellow smoky flame.

    The gas and kerosene stove used at home has inlet for air so that, burnt to given clean blue flame.
    Due to presence of small amount of nitrogen and sulphur, coal and petroleum produces carbon dioxide with oxides of nitrogen and sulphur which are major pollutant.

    2. Oxidation: Oxidation of ethanol in presence of oxidizing agents gives ethanoic acid.
    Carbon and its Compounds Class 10 Notes Science Chapter 4 21

    Oxidizing Agent: Some substances are capable of adding oxygen to others, are known as Oxidising Agent.
    Example: Alkaline KMnO4 (or KMnO4—KOH)
    Acidified K2Cr2O7 (or K2Cr2O7—H2SO4)
    KMnO4 – Potassium permanganate
    K2Cr2O7 – Potassium dichromate

    3. Addition Reaction: Addition of dihydrogen with unsaturated hydrocarbon in the presence of catalysts such as nickel or platinum or palladium are known as Hydrogenation (addition) reaction.
    Carbon and its Compounds Class 10 Notes Science Chapter 4 22

    Catalyst: Substances that cause a reaction to occur or proceeds to different rate without consuming in it are called a catalyst. For example; Ni, Pt, Pd, etc.

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