Hi there. I'm new to the forums, a freshman in college, and mainly asking this for the sake of understanding. Why does the MO theory cause lone pairs to bond? For example, in the Lewis sturcture of O2 there are 2 pairs of unbonded lone pair electrons which makes sense since both oxygen atoms completed their octet. In addition, the 2py and 2pz orbitals are used for overlapping in the valence bond theory, staying consistent with Lewis. But then in the MO theory, the (sigma)2s, (sigma)2s*, and (pi)2px are used to bond the electrons that were lone pairs. Why is this? I really want to understand this, but I'm having a lot of trouble putting together how the valence bond theory and MO theory fit together. Thank you for any input.