What order do you fill bonds?

[Grace_Aspinwall4J]

When drawing out a MO diagram when you are filling the slots for bonds down the center of the diagram do you completely fill (sigma p z) before you put a electron in (pi p x) or do you put one electron in (sigma p z) then one in (pi p x) then one in (pi p y) then you fill (sigma p z)?

[Wendy_Xie]

You fill the lowest one first, in this case it's the sigma 2pz, and then you put one in pi 2py and another one in pi 2px in the same spinning direction, then you go back to pi 2py and fill it with another electron which spins in the opposite direction of the two you already put in, and another electron in pi 2px.

Is that clear?

[amyjunus1A]

For this particular question, you fill up the specific energy levels before continuing on. Since pi and sigma bonds have different energy levels, you would fill up the (sigma pz) before the (pi px) and (pi py).

However, remember that there can be Z<8 or Z>/= 8, each which fills up the MO in slightly different ways. For Z>/=8, which seems to be the problem you are dealing with, the order goes from (sigma pz) to (pi px) and (pi py). For Z,8, the "filling order" goes from (pi px) and (pi py) to (sigma pz).

Hope that further clarifies! :)

[Grace_Aspinwall4J]

Thanks guys!