Chem

• Organic compounds are made up of carbon and form the basis of life of living organisms
• Allotropy is the phenomenon of the same element existing in different physical forms with similar chemical properties
• Different forms of an element are called allotropes
• Carbon, phosphorous, and sulphur exhibit allotropy
• Allotropes of carbon:

  • Diamond:
  • Each carbon atom is bonded to four other carbon atoms forming a rigid 3-dimensional structure
  • Hardest substance, not a conductor of electricity
  • Graphite:
  • Each carbon atom is bonded to three other carbon atoms in the same plane giving a hexagonal array
  • Soft and slippery, good conductor of electricity
  • Buckminsterfullerene:
  • Has carbon atoms arranged in the shape of a football
• Symbol of carbon: C

  Atomic number: 6

  Atomic mass: 12

  Electron configuration: 2,4

  Valency: 4

  Non-metallic element
• Synthetic diamonds can be produced by subjecting pure carbon to very high pressure and temperature
• Fullerene, e.g., C-60, has carbon atoms arranged in the shape of a football
• Carbon forms only covalent bonds because it has 4 valence electrons and to attain noble gas configuration, it shares 4 electrons with other carbon atoms or with atoms of other elements
• Covalent bond: Formed by sharing electrons between two atoms
• Physical Properties of Covalent Compounds:

  • Strong bonds within the molecule, but small intermolecular forces leading to low melting and boiling points
  • Electrons are shared between atoms, no charged particles are formed, hence poor conductors of electricity
  • Soluble in organic solvents but insoluble in water
  • Can exist as solid, liquid, or gaseous state
• Types of Covalent Bond:

  • Single covalent bond: When two electrons (1 pair) are shared between two atoms
  • Double bond: When four electrons (2 pairs) are shared between two atoms
  • Triple bond: When six electrons (3 pairs) are shared between two atoms
• Assertion (A): Diamond and graphite are allotropes of carbon. Reason (R): Some elements can have several different structural forms while in the same physical state. These forms are called allotropes.

  Assertion (A): Diamond is not a good conductor of electricity. Reason: It has no free electrons
• Identify the following:

  (i) An allotrope of carbon which has a two-dimensional layered structure consisting of flat hexagonal rings.

  (ii) An allotrope of carbon which looks like a soccer ball.

  (iii) An allotrope of carbon which contains both single and double bonds
• Carbon cannot make ionic compounds because it cannot gain or lose 4 electrons to form C4- or C4+ ions
• A covalent bond is a chemical bond formed by sharing electrons between two atoms
• Melting point and boiling point are low in covalent bonds because of small intermolecular forces
• Covalent compounds are poor conductors of electricity because electrons are shared between atoms, no charged particles are formed
• Carbon has the unique ability to form bonds with other atoms of carbon, giving rise to large molecules. This property is called catenation
• Carbon has a valency of 4 and can bond with four other atoms of carbon or atoms of some other mono-valent element
• Carbon forms covalent bonds with Oxygen, hydrogen, nitrogen, sulphur, chlorine, and many other elements, resulting in compounds with specific properties
• The reason for the formation of strong bonds by carbon is its small size, enabling the nucleus to hold on to the shared pair of electrons strongly
• Carbon-carbon bond is very strong and stable, while bonds formed by bigger atoms are much weaker
• Compounds made up of only Carbon and Hydrogen are called Hydrocarbons
• Saturated hydrocarbons have a single bond between the carbon atoms, like Alkanes with the general formula CnH2n+2
• Unsaturated hydrocarbons have a double or triple bond between carbon atoms, like Alkenes with the general formula CnH2n and Alkynes with the general formula CnH2n-2
• Nomenclature of Hydrocarbons:

  • Alkanes have the general formula CnH2n+2
  • Alkenes have the general formula CnH2n
  • Alkynes have the general formula CnH2n-2
• Classify the following compounds:

  • C2H4: Alkene
  • C3H4: Alkyne
  • C4H8: Alkene
  • C5H12: Alkane
  • C5H8: Alkene
  • C3H8: Alkane
  • C6H12: Alkane
• Draw the electron dot structure of ethyne and draw its bond structure
• Ethyne: Alkyne

  • Structural Formula: C2H2
  • Electron dot structure:

  1. C:::C:H

  • Bond Structure:

  1. C≡C-H