Given below are two statements :
Statement (I) : The first ionization energy of Pb is greater than that of Sn
Statement(II) : The first ionization energy of Ge is greater than that of Si .
In the light of the above statements, choose the correct answer from the options given below :
Statement (I) : The first ionization energy of Pb is greater than that of Sn
Statement(II) : The first ionization energy of Ge is greater than that of Si .
In the light of the above statements, choose the correct answer from the options given below :
- (A)Statement I is true but Statement II is false✓ Correct
- (B)Both Statement I and Statement II are false
- (C)Statement I is false but Statement II is true
- (D)Both Statement I and Statement II are true
Answer: (A)
Solution
Down Group 14, first ionization energy generally falls as atomic size increases: (roughly 1086, 786, 761, 709 and 716 kJ/mol). Between Sn and Pb the trend reverses: poor shielding by the filled and subshells in Pb raises its effective nuclear charge enough that , so statement I is correct.
Between Si and Ge, no comparable anomaly operates — the extra shielding from Ge's filled subshell is not enough to overturn the normal decreasing trend, so , making statement II false.
Between Si and Ge, no comparable anomaly operates — the extra shielding from Ge's filled subshell is not enough to overturn the normal decreasing trend, so , making statement II false.
JEE Main · 2025 · 24 Jan 2025 · Shift 2 · Single correct option