1s² 2s² 2p⁴

Here's how to understand it:

* 1s²: The first energy level (n=1) has one subshell, the s subshell, which can hold up to 2 electrons. Oxygen has 2 electrons in this subshell.

* 2s²: The second energy level (n=2) also has an s subshell, which again holds 2 electrons. Oxygen has 2 electrons in this subshell.

* 2p⁴: The second energy level also has a p subshell, which can hold up to 6 electrons. Oxygen has 4 electrons in this subshell.

Let me know if you'd like to see a more visual representation of this!