Anomalous first-member behaviour and the inert pair effect — NEET & JEE Questions

Question 1 · difficulty L1 · recall

The inert pair effect refers to the tendency of the outermost $ns^2$ electron pair in heavier p-block elements to

• A. remain less available for bonding
• B. become more reactive than all p electrons
• C. always be removed first
• D. form only ionic bonds

Question 2 · difficulty L2 · understanding

First members of p-block groups often show anomalous behaviour mainly because of their

• A. small size, high electronegativity and absence of accessible d orbitals in the valence shell
• B. very large size only
• C. low ionisation enthalpy only
• D. complete metallic character

Question 3 · difficulty L2 · understanding

The inert pair effect generally becomes more important

• A. down a p-block group
• B. from bottom to top only
• C. only in period 2
• D. only in noble gases

Question 4 · difficulty L2 · understanding

Because of the inert pair effect, heavier p-block elements often show increased stability of

• A. oxidation states two units lower than the group maximum
• B. only the highest oxidation state
• C. zero oxidation state only
• D. negative oxidation states exclusively

Question 5 · difficulty L3 · application

Which oxidation state becomes especially stable for thallium because of the inert pair effect?

• A. +1
• B. +2
• C. +3
• D. +5

Question 6 · difficulty L3 · application

For lead, the inert pair effect helps explain the relatively high stability of

• A. +2 compared with +4 in heavier chemistry
• B. +4 only
• C. +1 only
• D. +6

Question 7 · difficulty L3 · application

Why does nitrogen differ markedly from heavier Group 15 elements in some bonding patterns?

• A. Its small size and lack of valence d orbitals contribute to anomalous behaviour
• B. It is the largest Group 15 atom
• C. It has the strongest inert pair effect in the group
• D. It is metallic

Question 8 · difficulty L3 · application

Which statement best describes the trend in stability of Group 13 oxidation states down the group?

• A. The +1 state generally becomes more stable relative to +3
• B. The +3 state becomes exclusively more stable
• C. The +5 state becomes dominant
• D. Oxidation states become impossible

Question 9 · difficulty L4 · application

Why is $Pb^{4+}$ often a stronger oxidising species than $Pb^{2+}$?

• A. Pb(II) is stabilised by the inert pair effect, so Pb(IV) tends to be reduced to Pb(II)
• B. Pb(IV) contains no electrons
• C. Pb(II) is always unstable
• D. Pb(IV) cannot accept electrons

Question 10 · difficulty L4 · application

Which comparison best illustrates anomalous first-member behaviour?

• A. A second-period p-block element differs strongly from heavier congeners because of small size and inability to expand its valence shell
• B. The heaviest member exactly duplicates the first
• C. All group members have identical chemistry
• D. An anomaly must be caused only by nuclear mass