Hund's rule spin

1. Dec 7, 2008

atwong713

http://en.wikipedia.org/wiki/Image:Si_Hund.png

can someone help clarify something for me
in this diagram why is it that the arrow is placed in +1 first and in my text book it is placed in -1 first?

2. Dec 7, 2008

Staff: Mentor

Does it really matter? As long as there is no external magnetic field these orbitals are degenerated, so they can be occupied in any order.