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COMEDK2024Morning ShiftChemistryStructure of AtomActual

The mass number of an element X is 175 with 104 neutrons in its nucleus. Into which one of the following orbitals will the last electron enter?

Options

  1. A6s
  2. B5d
  3. C5f
  4. D4f

Correct answer

B. 5d

Step-by-step solution

Z = A - n = 175 - 104 = 71 Element with Z = 71 is Lutetium (Lu). After Xe ( Z = 54 ), 17 electrons are to be filled in order: 6s 4f 5d 6s gets 2, 4f gets 14, remaining 1 goes to 5d . Configuration: [Xe] 6s^2 4f¹⁴ 5d^1 The last electron enters the 5d orbital.

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