Chemistry: Chemical Bonding: Covalent Bond Parameters and Hydrogen Bonding (For CBSE, ICSE, IAS, NET, NRA 2022)

Glide to success with Doorsteptutor material for competitive exams : get questions, notes, tests, video lectures and more- for all subjects of your exam.

Covalent Bond Parameters

Bond Enthalpy

  • It is the amount of energy required for breaking one mole of a particular type of bonds in gaseous molecules.
  • It is also called bond dissociation enthalpy.
  • It is applicable to simple molecules which contain only one bond of the particular type.
  • For example, the bond enthalpy of Cl – Cl bond in Cl2 is 243 kJ mol – 1, of O = O in O2 is 498 kJ mol – 1 and of N ≡ N bond in N2 is 946 kJ mol – 1.
  • In H2O molecule two O – H bonds are present, and the two bonds require different amounts of energies to break.
The Two Bonds Require
  • The average bond enthalpy is defined as the average energy per bond required dissociating one mole of bonds in gaseous atoms. Its formula is given below:
Average Bond Enthalpy

The enthalpy value for some bonds is given below:

Bond Enthalpy

Hydrogen Bonding

  • It is a special type of attraction between a hydrogen atom which are bonded to a strong electro negative atoms like nitrogen, oxygen or fluorine and the unshared pair of electrons on another electronegative atom.
  • The hydrogen bond is a weak bond and its strength is about 4 - 25 kJ mol – 1.
  • It has less strength bonding as compared to the covalent bond, but it is strong enough to cause high boiling points in H2O and HF.
  • Water exists as a liquid because of the hydrogen bonding,
Water Exists Hydrogen Bonding
  • The electro negativity difference in hydrogen and the other electronegative atom causes the bond connecting them becomes polar in nature.
  • The hydrogen atom acquires a partial positive charge while the electronegative atom has partial negative charge.
  • The hydrogen bonding is formed from the electrostatic interaction between the positively charged hydrogen atom and the negatively charged electronegative atom.
  • There are two types of hydrogen bonds:
    • Intermolecular hydrogen bond: The hydrogen bond is formed between two different molecules. Eg: Water
    • Intramolecular hydrogen bond: When the hydrogen bond exists within the same molecule. Eg: Salicyldehyde and o-nitrophenol.
  • The hydrogen bonding plays an important role in the structure and function of many biomolecules such as proteins and nucleic acids.
Hydrogen Bonding

Developed by: