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The P-Block Elements

Question
CBSEENCH12006789

Why does NH3 form hydrogen bond but PH3 does not? 

Solution
Formation of hydrogen bonding depend on the size of  molecule. smaller the size greater the hydrogen bonding. Nitrogen has smaller size than phosphrous thus having a more abilty to form hydrogen bond.
N—H bond is reasonably polar and this leads to hydrogen bonding. As the bond polarity of the P—H bond is almost negligible, PH
3is not involved in hydrogen bonding.