Q. 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 :
A) Statement I is false but Statement II is true
B) Statement I is true but Statement II is false
C) Both Statement I and Statement II are true
D) Both Statement I and Statement II are false
Explanation
[Solution by Dr. Abubacker] Pb ($715.6$ kJ/mol) has a slightly higher first ionisation energy than Sn ($708.6$) because of the poor shielding of $4f$ electrons (lanthanoid contraction): Statement I true. Ge ($762$) is lower than Si ($786$): Statement II false. Answer (2).
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.