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Which of the following electron configurations is not allowed by the Pauli Exclusion Principle?

Option: 1


Option: 2


Option: 3


Option: 4


Answers (1)


The Pauli Exclusion Principle states  that in an atom none of the two electrons can have the four quantum numbers of similar set. Therefore, an electron configuration with only one electron in an orbital is not allowed because the second electron would have the same set of quantum numbers as the first, violating the Pauli Exclusion Principle. Thus, option A is not allowed. Option B is allowed because both electrons in the 1s orbital have opposite spins, satisfying the Pauli Exclusion Principle. Hence option B is correct.

Option A is incorrect because it has only one electron in the 1s orbital, which violates the Pauli Exclusion Principle. Hence option A is incorrect.

Option C is incorrect because the 2s orbital has a higher energy than the 1s orbital, so it should be filled after the 1s orbital is filled. Hence option C is incorrect.

Option D is incorrect because helium has only two electrons, which fill the 1s and 2s orbitals. Hence option D is incorrect.

Posted by

Sumit Saini

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