Here's why:

* Electron Configuration: The electron arrangement (2 6) tells us the number of electrons in each energy level.

* The first energy level (n=1) has 2 electrons.

* The second energy level (n=2) has 6 electrons.

* Atomic Number: The number of electrons in a neutral atom is equal to its atomic number. Oxygen has an atomic number of 8.

Let me know if you'd like to know more about electron configurations!