1s² 2s² 2p⁴

Here's a breakdown:

* 1s²: The first electron shell (n=1) contains two electrons in the s orbital (l=0).

* 2s²: The second electron shell (n=2) contains two electrons in the s orbital (l=0).

* 2p⁴: The second electron shell also contains four electrons in the p orbitals (l=1). The p orbital has three sub-orbitals (px, py, pz), each capable of holding two electrons. In oxygen, these sub-orbitals are filled with two electrons each, except for one sub-orbital which contains only one electron.

This arrangement can also be represented in a more visual way using the following orbital diagram:

```

2p ↑↓ ↑ ↑

2s ↑↓

1s ↑↓

```

This arrangement reflects the fact that oxygen has six electrons in its outermost shell (n=2), making it a highly reactive element.