Question 4 • *26-27 CFISD TX-Chemistry A CR
The configuration 1s² 2s² 2p⁶ 3s² lists every occupied subshell from the beginning, so it is longhand notation. Noble-gas notation would replace the first ten electrons, 1s² 2s² 2p⁶, with [Ne], giving [Ne] 3s².
AI-written and checked against the verified answer.