MCQEasyJEE 2024Electronic Configuration

JEE Chemistry 2024 Question with Solution

The electronic configuration for Neodymium is: (Atomic Number for Neodymium 6060)

  • A

    [Xe]4f46s2[Xe] \, 4f^4 \, 6s^2

  • B

    [Xe]5f47s2[Xe] \, 5f^4 \, 7s^2

  • C

    [Xe]4f66s2[Xe] \, 4f^6 \, 6s^2

  • D

    [Xe]4f55d16s2[Xe] \, 4f^5 \, 5d^1 \, 6s^2

Answer

Correct answer:A

Step-by-step solution

Standard Method

Given: Neodymium (Nd) has atomic number 6060.

Find: The correct electronic configuration of Nd.

Neodymium is a lanthanide, so we use the xenon core and then place the remaining electrons in the appropriate subshells.

Using the noble gas core:

[Xe]=1s22s22p63s23p64s23d104p65s24d105p6[Xe] = 1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^{10} 4p^6 5s^2 4d^{10} 5p^6

After [Xe][Xe], the remaining electrons occupy the 4f4f and 6s6s orbitals. Therefore:

[Xe]4f46s2[Xe] \, 4f^4 \, 6s^2

This matches option A. Therefore, the correct electronic configuration is [Xe]4f46s2[Xe] \, 4f^4 \, 6s^2.

Option Verification

Given: We must identify the correct condensed electronic configuration of Neodymium.

Find: Which option matches the lanthanide configuration for atomic number 6060.

Check the options against the lanthanide filling pattern:

  • [Xe]4f46s2[Xe] \, 4f^4 \, 6s^2 matches the derived configuration.
  • [Xe]5f47s2[Xe] \, 5f^4 \, 7s^2 is incorrect because 5f5f filling belongs to actinides, not neodymium.
  • [Xe]4f66s2[Xe] \, 4f^6 \, 6s^2 has too many electrons in 4f4f for Nd.
  • [Xe]4f55d16s2[Xe] \, 4f^5 \, 5d^1 \, 6s^2 does not match the stated solution conclusion for this question.

Hence, the correct option is A.

Common mistakes

  • Students often confuse lanthanides with actinides and choose a configuration containing 5f5f electrons. This is incorrect because neodymium is a lanthanide, so the relevant subshell is 4f4f, not 5f5f.

  • A common mistake is counting the electrons after [Xe][Xe] incorrectly. Since [Xe][Xe] accounts for 5454 electrons, only 66 electrons remain for Nd. Distribute them as 4f46s24f^4 6s^2.

  • Some students assume all remaining electrons go into 4f4f and forget the 6s26s^2 electrons. The condensed configuration must include both occupied subshells beyond [Xe][Xe].

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