Homonuclear diatomic molecules molecular orbital MO theory

In a diamagnetic species, all electrons are spin-paired a diamagnetic substance is repelled by a magnetic field. A paramagnetic species contains one or more unpaired electrons a paramagnetic substance is attracted by a magnetic field. 

13 Homonuclear diatomic molecules molecular orbital (MO) theory 

---

Valence bond theory does agree fairly well with molecular orbital (MO) theory for homonuclear diatomic molecules that can obey the octet rule H2 (single bond, bond order = 1), Li2 (single bond, bond order = 1), N2 (triple bond, bond order = 3), 02 (double bond, bond order = 2), F2 (single bond, bond order = 1). However, for those molecules that don t, it is more difficult to know if they exist or not and what bond orders they have. MO theory allows us to predict that He2, Be2 and Ne2 do not exist since they have bond orders = 0, and that B2 has bond order = 1 and C2 has bond order = 2. 

Molecular Orbital (MO) Theory and Electron Delocalization Central Themes of MO Theory Homonuclear Diatomic Molecules of the Period 2 Elements... 

Just as we treated the bonding in H2 by using molecular orbital theory, we can consider the MO description of otiier diatomic molecules. Initially we will restrict our discussion to homonuclear diatomic molecules (those composed of two identical atoms) of elements in flie second row of the periodic table. As we will see, die procedure for determining the distribution of electrons in these molecules closely follows the one we used for H2. 

---