1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹
Explanation:
* 1s²: The first energy level (n=1) has one sublevel (s) which can hold a maximum of 2 electrons.
* 2s²: The second energy level (n=2) has an s sublevel that holds 2 electrons.
* 2p⁶: The second energy level (n=2) also has a p sublevel that can hold up to 6 electrons.
* 3s²: The third energy level (n=3) has an s sublevel that holds 2 electrons.
* 3p⁶: The third energy level (n=3) also has a p sublevel that holds 6 electrons.
* 4s¹: The fourth energy level (n=4) has an s sublevel that holds 1 electron. This is potassium's valence electron.
Important Note: The 4s orbital fills before the 3d orbital because the 4s orbital has a lower energy level. This is why potassium has a single electron in its outermost shell.
