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CBSE Guess > Papers > Important Questions > Class X > 2014 > Chemistry > Chemistry By Mrs. Kritika Bhola

CHEMISTRY CBSE CLASS X

Carbon and Its Compounds

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CARBON

  • An element
  • A non-metal
  • Present in earth’s crust- 0.02% ( in form of minerals – carbonates, coal, petroleum, etc.) an din atmosphere – 0.03% ( CO2 )
  • Present in all living things – ( Carbon compounds---- Organic  Compounds)
  • Always forms Covalent bonds.
  • Is tetravalent
  • Occurs in both free and combined state.

COVALENT  BONDS
At. no. is 6  ----  K-2 ; L-4 ----- To become stable it should either gain 4 electrons or lose 4 electrons.

  • It cannot gain 4 electrons - It would be  difficult for nucleus with 6 protons to hold 10 electrons.
  • It cannot lose 4 electrons -  It would require large amount of energy to remove 4 electrons .

This problem is overcome by sharing its valence electrons with other atoms of carbon or with atoms of other elements.

  • Covalent bonds are very strong and do not break easily because the carbon atoms are very small in size  due to which their nuclei hold the shared pair of electrons between atoms strongly .

CARBON IS TETRAVALENT
Tetra - 4 ; Valent – valency

SELF COMBINATION  (Catenation)

Carbon atoms form long chains which are useful to us as we can derive large no. of carbon compounds.

  • Carbon compounds are exceptionally stable as they form strong bonds among themselves and with other elements.

OCCURRENCE OF CARBON

  • In free state  --- Diamond , Carbon, Buckminsterfullerene
  • In combined state ----  In form of compounds
    1. CO2 in air
    2. Carbonates ( limestone, marble, chalk)
    3. Fossil fuels ( coal , petroleum, natural gas)
    4. Organic compounds ( carbohydrates, fats and proteins)
    5. Wood, cotton wool, etc.

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Submitted By Mrs. Kritika Bhola
Email Id : kritikabhola@yahoo.co.in