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JAMB Chemistry 2025 Objective — Question 15

Question 15 of 40 from the Joint Admissions and Matriculation Board (JAMB) Chemistry 2025 Objective paper, with the correct answer and a full explanation.

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The second ionisation energy of sodium is much greater than the first because

  • A. The second electron is far from the nucleus
  • B. Sodium has a larger radius after losing one electron
  • C. The second electron is removed from a noble gas configurationCorrect
  • D. Sodium becomes more metallic on ionisation

Explanation

Na is 1s²2s²2p⁶3s¹. First IE removes the outer 3s electron. Na⁺ has noble gas config (1s²2s²2p⁶). The second IE must remove an electron from this stable filled shell, requiring much more energy.

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