Z>8, Z<8

[Jane Sin 3A]

I know Z is nuclear charge, and I know the consequent shape of the molecular orbital diagram, but I am confused with how we calculate the value of Z. Am I right in saying that the Z value is found from the number of valence electrons from the p orbital? For example, O2 has 4+4 electrons in the p orbital, so it has 8 electrons, and thus counts as Z>8? And N2 has 3+3 electrons in the p orbital, and is thus 6 for Z and Z<8?

[vsyacoubian2A]

Z stands for atomic number. So it means that elements that have an atomic number less than 8 or greater than 8 have a certain molecular orbital structure.

[Jane Sin 3A]

Then can you explain why NO+ has a molecular orbital diagram that corresponds to z<8?

[Elan Karlin Dis3H]

It is because both these atoms have less than eight valence electrons

[shannon_tseng_3L]

what would happen if one atom in a molecule has atomic number greater than 8 and the other has Z less than 8?

[Jane Sin 3A]

Okay so I found out from my discussion today that only HOMONUCLEAR problems (same atoms,e.g. O2) need the whole z>8 or z<8 thing. Heteronuclear (different atoms, e.g. NO) will always be a certain order, unconcerning z. So, for homonuclear problems, you just check the atomic number (z) to find out if z is greater than or less than 8. So, O2 has an atomic number of 8 (because O has an atomic number of 8). Basically, elements H through N are Z<8, and O to F are Z>8.

[Jane Sin 3A]

Heteronuclear problems like NO will always have a shape like Z<8.

[Kristina Mercolino 3C]

Why does an atom with an atomic number >/= 8 have the 2pi and 2 sigma orbitals switch? What is the reason for this switch?

[Alejandra_Vasquez_1B]

As long as one atom in the compound is less than 8, then you will have to use the z<8 diagram. It doesn't matter if one atom is greater than 8, you still have to use the z<8 diagram because of the atom that is less than 8.