Which rule is violated in the electronic configuration ${{1s}^{0}}$ ${{2s}^{2}}$ ${{2p}^{4}}$?

[prasanna]

Aufbau principle is violated in this electronic configuration because according to Aufbau principle, electron enters into orbital of lowest energy. Among Is, 2s and 2p, Is has least energy. So 1s orbital must be filled before the electron should enter into 2s.

[Sai1]

Please explain this rule with an example mam