1s² 2s² 2p⁴

Here's how to break it down:

* 1s²: The first energy level (n=1) has one sublevel, the 's' sublevel. It can hold a maximum of 2 electrons, and oxygen has 2 electrons in this sublevel.

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

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

Important Note: The 'p' sublevel actually has three orbitals (px, py, and pz), each of which can hold a maximum of 2 electrons. So, the full breakdown of the 2p⁴ configuration would be 2pₓ² 2pᵧ¹ 2p₂¹ (with one orbital having 2 electrons and the other two having one each).