In which of the fallowing molecule have first higher enthalpy of formation ($∆$H_f ) of   in 15^th group hydrides( EH₃)

A=NH₃, B= PH₃, C=AsH₃, D= SbH₃  E= BiH₃

All the elements of Group 15 form hydrides of the type EH₃ where E = N, P, As, Sb or Bi. The hydrides show regular gradation in their properties. The stability of hydrides decreases from NH₃ to BiH₃ which can be observed from their bond dissociation enthalpy. Consequently, the reducing character of the hydrides increases. Ammonia is only a mild reducing agent while BiH₃ is the strongest reducing agent amongst all the hydrides. Basicity also decreases in the order NH₃ > PH₃ > AsH₃ > SbH₃ > BiH₃. Due to high electronegativity and small size of nitrogen, NH₃ exhibits hydrogen bonding in solid as well as liquid state. Because of this, it has higher melting and boiling points than that of PH₃ .

Central atom size order :NH₃ < PH₃ < AsH₃ < SbH₃  < BiH₃

Bond length order: NH₃ < PH₃ < AsH₃ < SbH₃  < BiH₃

Bond energy order :NH₃ > PH₃ > AsH₃ > SbH₃ > BiH₃

Enthalpy of formation order:NH₃ > PH₃ > AsH₃ > SbH₃ > BiH₃

Bond angle order : NH₃ > PH₃ > AsH₃ > SbH₃ > BiH₃

Thermal stability order : NH₃ > PH₃ > AsH₃ > SbH₃ > BiH₃

Basic nature order :NH₃ > PH₃ > AsH₃ > SbH₃ > BiH₃

Reducing power order :NH₃ < PH₃ < AsH₃ < SbH₃  < BiH₃

H- bonding capacity order : NH₃ > PH₃ > AsH₃ > SbH₃ > BiH₃

Central atom electro negativity order :NH₃ > PH₃ > AsH₃ > SbH₃ > BiH₃

S-character percentage at central atom order : NH₃ > PH₃ > AsH₃ > SbH₃ > BiH₃

Melting point order :  PH₃ < AsH₃  < SbH₃  < NH₃< BiH₃

Boiling point order : PH₃ < AsH₃ <NH₃  < SbH₃  < BiH₃

vapourisation order : PH₃ > AsH₃ > SbH₃ > NH₃ >BiH₃

Enthalpy of vapourisation :  PH₃ < AsH₃  < SbH₃  < NH₃< BiH₃