Periodic Table and PeriodicityhardMCQ SINGLE⭐ Must-Do

Which of the following correctly describes the relationship between the first ionization energy () aPeriodic Table and Periodicity Chemistry Question

Question

Which of the following correctly describes the relationship between the first ionization energy ($IE_1$) and the second ionization energy ($IE_2$) of Copper ($Cu$) compared to Potassium ($K$)?

Answer: B

💡 Solution & Explanation

$IE_1(Cu) > IE_1(K)$ due to higher $Z_{eff}$. However, $IE_2(K) \gg IE_2(Cu)$ because removing the second electron from $K^+$ requires breaking a highly stable noble gas core ($3p^6$), whereas $Cu^+$ only has a pseudo-noble gas core ($3d^{10}$).

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