MCAT General Chemistry Question 19: Answer and Explanation

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Question: 19

4. Ionization energy contributes to an atom's chemical reactivity. Which of the following shows an accurate ranking of ionization energies from lowest to highest?

  • A. first ionization energy of Be < second ionization energy of Be < first ionization energy of Li
  • B. first ionization energy of Be < first ionization energy of Li < second ionization energy of Be
  • C. first ionization energy of Li < first ionization energy of Be < second ionization energy of Be
  • D. first ionization energy of Li < second ionization energy of Be < first ionization energy of Be

Correct Answer: C

Explanation:

Ionization energy increases from left to right, so the first ionization energy of lithium is lower than that of beryllium. Second ionization energy is always larger than first ionization energy, so beryllium's second ionization energy should be the highest value. This is because removing an additional electron from Be+ requires one to overcome a significantly larger electrostatic force.

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