When hydrogen is bonded with a highly electronegative element such as Nitrogen,
Oxygen or Fluorine, the molecule will be polarized and a dipole is produced. The slightly positive hydrogen atom is attracted by the slightly negative charge electronegative atom.
An electrostatic attraction between the neighboring molecules is set up when the positive pole of one molecule attracts the negative pole of the neighboring molecule.
This type of force which involves hydrogen is known as Hydrogen Bonding.
Hydrogen bonding causes the association of molecules with each other.
The common examples of Hydrogen Bonding are H20 and HF;
Effect of Hydrogen Bonding;
The hydrogen bonding is the strongest of the secondary bonds, but it is much weak than a covalent bond.
The hydrogen bonding greatly affects the physical properties of a compound. Due to this bond the melting point, boiling point, density and viscosity of a compound are increased in a great extent.
The most interesting impact of hydrogen bonding is seen in crystalline structure of ice which causes water to behave abnormally from 0°c – 4°C (anomalous behavior). The density of ice is less than liquid water. When ice melts some of the hydrogen bonds are broken and the molecules pack more closely together so that water has a high density.
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Chapter 4 – Multiple Choice Questions