# Molecular orbitals of CH2 an SLACs

I was wondering about molecular orbitals of methylene different states 1B1 3B1 1A1 and how are they connected to symmetry point group lower case 1a1, etc orbitals what those numbers and alphabets mean?

It would be great if someone can derive those orbitals from symmetry and show me which states 1B1, 3B1 and 1A1 are referred to and what does up script, subscripts and alphabets stand for and connect them to lower case 1a1 ,etc.

• May 1, 2015 at 13:50

The first question to always ask when you are trying to build an MO diagram is what point group does my molecule fall into? In this case, the $\ce{CH2}$ molecule has C2V symmetry (like the water example shown above). Each of the atomic orbitals (AO's) on carbon (left) and the combination of $1s$ orbitals on the hydrogen atoms (right) has a symmetry label that corresponds to one of the irreducible representations of the point group.