The elements of group 15 combines with oxygen directly or indirectly to form different types of oxides.

Oxidation state of central atom N P As Sb Bi
+5 N2O5 P4O10 As2O5 Sb2O5 Bi2O5
+4 N2O4, NO2 P4O8
+3 N2O3 P4O6 As2O3 Sb2O3 Bi2O3
+2 NO
+1 N2O

Nature of oxides
All the oxides of nitrogen and phosphorus are strongly acidic in nature (except NO and N2O); oxides of arsenic are weakly acidic; oxides of antimony are amphoteric and oxides of bismuth are weakly basic. This can be explained on the basis of increase in size of central atom. In lower element oxides, atom has small size and it can more strongly pulls the electron pair between O-H bond in water and thus helps in release of H+ ions.

Formation of oxides
1. Formation of oxides of nitrogen

The p Block Elements Chemistry Notes

2. Formation of oxides of phosphorus
The p Block Elements Chemistry Notes

The oxides of As(III) and Sb (III) can also be prepared by heating these elements in air.

3. Structures of oxides
The p Block Elements Chemistry Notes

Illustration 1.
The reddish brown coloured gas formed when nitric oxide is oxidized by air is
(A) N2O5 (B) N2O4
(C) NO2 (D) N2O3
Solution: (C)

Illustration 2.
Which of the following oxides is the most acidic?
(A) N2O5 (B) P2O5
(C) As2O5 (D) Sb2O5
Solution: (A)

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