why chromium has an exceptional confirugation Explain with the help of orbital diagram showing the exchange of energy
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Explanation:
Why are Cr and Cu called exceptional configurations?
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6 Answers

Khushi Sharma, lives in New Delhi
Answered July 4, 2017
When we write the electronic configuration of Cr (24) as per the ‘Aufbau principle’ the 3d orbital contains 4 electrons and the 4s orbital contains 2 electrons. Since, the d sub shell can have maximum 10 electrons therefore either 3d^10 is stable or 3d^5. Since, every element prefers to have a stable configuration hence one electron from 4s orbital will get transferred into the 3d orbital. Thus, it has an exceptional configuration.
Similarly, in the case of Cu (29) 3d orbital has 9 electrons and 4s has 2. But, to get a stable configuration, 1 electron from 4s will get transferred into 3d giving it an exceptional electronic configuration of (Ar)3d^10 4s^1.
Remember that these 2 cases are exceptional only when the element is in its ground state.