1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹

Here's a breakdown:

* 1s²: The first energy level (n=1) has 2 electrons in the s orbital.

* 2s² 2p⁶: The second energy level (n=2) has 2 electrons in the s orbital and 6 electrons in the p orbital.

* 3s² 3p⁶: The third energy level (n=3) has 2 electrons in the s orbital and 6 electrons in the p orbital.

* 4s¹: The fourth energy level (n=4) has 1 electron in the s orbital.

Important Note: You might see the electron configuration written as [Ar]4s¹ This is a shorthand notation where "[Ar]" represents the electron configuration of Argon (the preceding noble gas), which is 1s² 2s² 2p⁶ 3s² 3p⁶.