How to determine which orbital has less energy when drawing an MO Energy Diagram

[Junghyuk_Park_1I]

I was wondering how you determine which orbital is less energy when drawing a molecular orbital energy diagram (i.e. N 2s vs. O 2s)? Thank you in advance.

[EmmaSaid3C]

I believe that the more electronegative atom has a lower energy level.
So in that case, oxygen would have a lower energy level than nitrogen because oxygen is more electronegative.

[PriscillaMariscal_3F]

One of my TA's also told me that another way of determining which orbital is less energy, is by asking yourself which element has a higher Z value. The higher the Z value, the lower in energy it'll be.