Why Does the Ni+ Ion Have an Electron Configuration of [Ar]3d9?

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SUMMARY

The electron configuration of the Ni+ ion is [Ar]3d9, contrary to the initial assumption of [Ar]4s13d8. This discrepancy arises because, upon ionization, one electron is promoted from the 4s orbital to the 3d orbital. The energy dynamics change due to electron shielding effects, where the 3d orbitals experience greater shielding than the 4s, leading to a higher binding energy for 3d in heavier transition metals. Quantum-mechanical calculations, such as those performed using Cowan's code, are essential for accurately determining these configurations.

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thonwer
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Homework Statement


Which is the electron configuration of the Ni+ ion?

Homework Equations


Ni : [Ar]4s23d8

The Attempt at a Solution


Ni+: [Ar]4s13d8

Apparently this solution is wrong and should be Ni+: [Ar]3d9 but I do not know why. As far as I know 4s has less energy than 3d so, why does one electron promote from 4s to 3d after one ionization?
 
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This kind of thing is subtle. The only way to solve this kind of problems is by quantum-mechanical calculations, for example Cowan's old code.

In hydrogen, all orbitals with the same principle quantum number have (almost) the same energy. But when there are more electrons, the "circular" 3d orbitals are shielded much more than s-electrons, which makes that 4s is filled before 3d in transition metal atoms.

In heavier atoms, the 3d binding energies are larger than 4s, 4p, 4d, 4f.
 

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