Question

Give reason for the following: 

(i) Red phosphorus is less reactive than white phosphorus 

(ii) Electron gain enthalpies of halogens are largely negative.

(iii) N₂O₅ is more acidic than N₂O₃.

Answer 1

(i) Red phosphorous being polymeric is less reactive than white phosphorous which has discrete tetrahedral structure.

(ii) They readily accept an electron to attain noble gas configuration.

(iii) Because of higher oxidation state (+5) of nitrogen in N₂O₅

_{Detailed Answer:} 

_{(i) White phosphorus is formed of discrete P4 tetrahedra which with very high angular strain while red phosphorus is a polymer of P4 tetrahedra with lesser angular strain. This high angular strain results in unstability of white phosphorus and high reactivity.}  

_{(ii) Halogens are smallest in size in their respective periods resulting in high effective nuclear charge. They accept one electron to attain noble gas electronic configuration. Hence, they have negative electron gain enthalpy.}

(iii) Oxidation state of N in N₂O₅ =+5

Oxidation state of N in N₂O₃ =+3

As N has higher oxidation state in N₂O₅, therefore it is more acidic