Differentiating between shapes of structure

[Elle_Bertuccelli_1B]

When constructing a MO structure, I know that there are two different ones for a certain value of Z. Does Z refer to atomic number? What if one element of a compound has Z>8 and one has Z<8?

[Mirna_Velasco_1L]

Yes, Z refers to atomic #. For example elements in period 1 and period 2 up to Nitrogen with a Z of 7, we draw the molecular energy level diagram with Z <8. Thus, for elements like Oxygen and Flourine we draw the diagram with Z is greater or equal to 8. Also, if I recall correctly, I remember Dr. Lavelle saying if we are given a compound that has Z <8 and one has Z greater or equal to 8 (such as (NO)) than we use the Z <8 diagram. Also because Oxygen has lower energy due to its higher electronegativity, the bonding atoms will be closer to O than to N. I hope this helps, I tend to be bad at explaining concepts :)