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The d-and f-Block Elements — Chemistry STD 12 Science — Question

Gujarat BoardEnglish MediumSTD 12 ScienceChemistryThe d-and f-Block Elements2 Marks
Question
Why the chromium and copper have exceptional electronic configuration?
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Answer

→ There is little energy difference between (n-1)d and ns orbitals.
Furthermore, half and completely filled sets of orbitals are relatively more stable.
→ A consequence of this factor is reflected in the electronic configurations of Cr and Cu in the 3d series.
→In case of Cr
${ }_{24} Cr :[ Ar ] 3 d^5 4 s^1$ instead of $[ Ar ] 3 d^4 4 s^2$
→ The energy gap between the two sets (3d and 4s) of orbitals is small enough to prevent electron entering the 3d orbitals.
→ Similarly in case of Cu,
${ }_{29} Cu :[ Ar ] 3 d^{10} 4 s^1$ instead of $[ Ar ] 3 d^9 4 s^2$

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