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Orbitals fill in the following order, 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, etc. Its a nice pattern that many elements follow, but there are exceptions to. For example:
V: 1s2 ... 4s2 3d3
Cr: 1s2 ... 4s1 3d5
And not: (which would seem to be breaking pattern)
Cr: 1s2 ... 4s2 3d4
This can also be seen on other elements, where a higher shell 'steals' from one below it in a seemingly random order. Is there a reason behind this, and if so, even if complex, what pattern is there to it?
I am new to the world of the very small, new to chemistry. Any help is greatly appreciated.