(a) Give reasons for the following: (i) Bond enthalpy of F2 is lower than that of Cl2. (ii) PH3 has a lower boiling point than NH3. (b) Draw the structures of the following molecules: (i) BrF3 (ii) (HPO3)3 (iii) XeF4

a) i. Fluorine has lower bond enthalpy than chlorine. This happens because the size of fluorine is small and F-F bond length is short. Due to this the electrons lie in 2p orbital with large electron-electron repulsion among the lone pairs of F2 molecule but they are relatively much closer to each other in Cl2 molecule.
ii. This is due to the fact that NH3 has hydrogen bonding which increase the bond strength, thus, increases the boiling point, while in case of PH3 Van der Waal's forces are weaker.
b. The structures of the following molecules are: