4d instead of 3d

File in which the problem appears

LCAO model

Problematic sentence

Therefore shell-filling order is 1s, 2s, 2p, 3s, 3p, 4s, 4d, ..

Correct version

Therefore shell-filling order is 1s, 2s, 2p, 3s, 3p, 4s, 3d, ..