Consider the following elements In, Tl, Al, Pb, Sn and Ge. The most stable oxidation states of elements with highest…
p-Block Elements (Class 12) · Class 12 · JEE Main Previous Year Question
Consider the following elements In, Tl, Al, Pb, Sn and Ge. The most stable oxidation states of elements with highest and lowest first ionisation enthalpies, respectively, are:
- a
and
- b✓
and
- c
and
- d
and
and
Step 1 — Identify elements with highest and lowest IE₁
Among In, Tl, Al, Pb, Sn, Ge:
First ionisation enthalpies (approximate):
- Al: ~577 kJ/mol
- Ge: ~762 kJ/mol
- Sn: ~709 kJ/mol
- Pb: ~716 kJ/mol
- In: ~558 kJ/mol
- Tl: ~589 kJ/mol
Highest IE₁: Ge (~762 kJ/mol) — due to small size and effective nuclear charge in period 4 Lowest IE₁: In (~558 kJ/mol) — large size, shielding
From official solution (Image 6): Among Al, In, Tl, Ge, Sn, Pb — highest IE₁ is Ge, lowest is In.
Step 2 — Most stable oxidation states
- Ge (Group 14): inert pair effect is weak → most stable OS = +4
- In (Group 13): inert pair effect → most stable OS = +3
Answer: +4 (Ge) and +3 (In) → Option (b)
Key Points:
- Ge: highest IE₁ among the given elements; most stable OS = +4
- In: lowest IE₁; most stable OS = +3
- Inert pair effect increases down group 13 and 14
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