Simple electronic configuration question.

[cantgetaname]

Why is something like Fluorine written as $$1s^{2}\;\;2s^{2}\;\;2p_{x}^{2}\;\;2p_{y}^{2}\;\;2p_{z}^{1}$$ and not $$1s^{2}\;\;2s^{2}\;\;2p_{x}^{2}\;\;2p_{y}^{1}\;\;2p_{z}^{2}$$?

$$2p_{y}^{1}$$ and $$2p_{z}^{1}$$ should be of the same energy, right?

Or is it only a matter of convenience/convention which one we write?

 

[chemisttree]

Where do you see fluorine written this way. I always thought the various suborbitals (x,y,z) of the p orbitals were degenerate so any way you write it would be OK but why would you choose one over the others? I've never seen it written this way.