Answer the question on the basis of passage given below:
Second period elements of p-Block differ from the rest of their group members due to their small atomic size, high electronegativity, high ionization enthalpy and absence of d-orbitals.
The elements from the second period like C, N, O have unique property of forming pπ–pπ multiple bonds whereas other heavier elements of p-block form dπ–pπ multiple bonds. This changes the properties of second period elements to great extent. Also the single bond strength of the p-block elements with their own atoms gets affected by their atomic size and presence of lone pairs.
Inert pair effect also affects the properties of the p-Block elements especially for those elements which are present from 4th period onward and this happens due to poor screening effect of inner (n–1)d subshell electrons.
Among the elements mentioned below, some are not stable in their +3 oxidation state and undergo disproportionation reactions easily
A. N
B. P
C. As
D. Sb
E. Bi
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → N and P only
An element whose +3 state is unstable changes into a higher and a lower oxidation state at the same time (disproportionation). In group 15 the +3 state becomes more stable down the group (inert pair effect), so only the lighter elements disproportionate.
A. N — Correct. All the oxidation states of nitrogen from +1 to +4 tend to disproportionate in acid solution; nitrous acid (+3) gives nitric acid (+5) and NO (+2).
B. P — Correct. Nearly all intermediate oxidation states of phosphorus, including +3, disproportionate into +5 and −3. On heating, phosphorous acid gives phosphoric acid and phosphine:
\( \ce{4H3PO3} \xrightarrow{\Delta} \ce{3H3PO4 + PH3} \)
C. As — Incorrect. The +3 state of arsenic is stable with respect to disproportionation.
D. Sb — Incorrect. The +3 state is still more stable for antimony.
E. Bi — Incorrect. For bismuth +3 is the most stable oxidation state, because of the inert pair effect.
NCERT (Pre-rationalised edition, 2022-23):
Chemical Properties
