inner shell electrons

[BrownieDDD]

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I know outer shell electrons are valence electrons, and inner are core. But when it comes to electronic configuaraionts like

1s2 2s2 2p6 3s2 3p6 4s2 3d3 of vanadium, which specifically are the inner and outer?.. Does it relate to the energy levels n=1, n=2 etc,.

if 4s2 is the outer shell electorns, how...it fills FIRST before 3d3.......