What is a hydrogen bond? Explain its characteristics with examples.

(N/A) hydrogen bond is an attractive force present between a partially positive $H^{\delta+}$ ion and a partially negative atom (like $N, O, F$) in molecules.
Examples: $(i)$ $N-H$ bond in $NH_3$,$(ii)$ $O-H$ bond in $H_2O, C_2H_5OH, C_6H_5OH$,$(iii)$ $H-F$ bond in $HF$,$(iv)$ $o-$chlorophenol.
Characteristics:
$\Rightarrow$ Although hydrogen bonding is primarily limited to $N, O, F$,species such as $Cl$ may also participate in hydrogen bonding under specific conditions.
$\Rightarrow$ The energy of a hydrogen bond varies between $10$ to $100 \ kJ \ mol^{-1}$.
$\Rightarrow$ This is a significant amount of energy; therefore,hydrogen bonds are a powerful force in determining the structure and properties of many compounds,such as proteins and nucleic acids.
$\Rightarrow$ The strength of the hydrogen bond is determined by the coulombic interaction between the lone-pair electrons of the electronegative atom of one molecule and the hydrogen atom of another molecule.
$\Rightarrow$ As the distance between molecules in the same substance increases,the strength of the hydrogen bond decreases (e.g.,$Solid$ $\rightarrow Liquid$ $\rightarrow Gas$).