Question

Among \[\begin{align}& \text{N}{{\text{H}}_{3}},\text{ }{{\text{H}}_{2}}\text{O and HF} \\
 & \\ \end{align}\], which would you expect to have the highest magnitude of hydrogen bonding and why ?

Answer 1

Hint: Hydrogen bond is formed between hydrogen bonds i.e. present between those pairs of atoms which have a high electron affinity, mainly these atoms belong to the second-row elements such as nitrogen, oxygen and fluorine. It depends on the electronegativity of an atom and the amount of hydrogen atom present.

Complete step by step answer:
- Electronegativity is the tendency of an atom to attract the shared pair of electrons from the less electronegative atom.
- Whereas electron affinity of an atom is the amount of energy which is released when an electron
Attaches to a neutral atom.
- From oxygen, fluorine and nitrogen, fluorine is the most electronegative element because along the period electronegativity increases and down the group, it increases.
So, the increasing order of electronegativity will be:
N < O < F
- So, according to the order, HF should have the highest magnitude of hydrogen bonding but it is not true.
- The amount of H-atom also matters. In the case of water, there are enough H- atoms present for the oxygen to form H - bonds.
- But in the case of HF, there is less no. of H-bonds.
- Also, in ammonia, the hydrogen bond is formed through the lone pair that is present on nitrogen, but it is also present in limited amounts and cannot satisfy all the hydrogen bonds.
So, the order of the highest magnitude of hydrogen bonding will be:
${{\text{H}}_{2}}\text{O}$ > $\text{HF}$ > $\text{N}{{\text{H}}_{3}}$

Therefore, water has the highest magnitude of hydrogen bonding.

Note: There are two types of hydrogen bonds i.e. intermolecular, which take place between different molecules and intramolecular, which take place in the same molecule by the different parts. ${{\text{H}}_{2}}\text{O}$, $\text{N}{{\text{H}}_{3}}$ and HF are examples of intermolecular hydrogen bonding.