Nitrogen, oxygen and fluorine are the highly electronegative elements. when they are attached to form covalent a hydrogen atom to bond, the electrons of the covalent bond; shifted towards more the electronegative atom. This partially positively charged hydrogen atom forms a bond with the other more electronegative atom. This bond is known as

Nitrogen, oxygen and fluorine are the highly electronegative elements. When they are attached to a hydrogen atom to form covalent bond, the electrons of the covalent bond are shifted towards the more electronegative atom. This partially positive charged hydrogen atom forms a bond with the other more electronegative atom. This bond is known as hydrogen bond and is weaker than the covalent bond, e.g., in HF molecule,

$---{\mathrm{H}}^{{\mathrm{\delta }}^{+}}-{\mathrm{F}}^{{\mathrm{\delta }}^{-}}---{\mathrm{H}}^{{\mathrm{\delta }}^{+}}-{\mathrm{F}}^{\mathrm{\delta }-}---\mathrm{H}{}^{{\mathrm{\delta }}^{\pm }}-{\mathrm{F}}^{\mathrm{\delta }-}---$