[redfox]

I'm trying to teach myself about boundary surfaces, molecular orbitals, etc. but I'm a bit confused about lobes. I've read that CO, for example, can act as an electron donor, but only a weak donor due to the small size of the lobe. How do I know if there is a large or small lobe?
Also, the sigma_s^b (not sure where to find sigma symbol on here) orbital in CO has more oxygen character so lobes are weighted towards the oxygen atom.
Can someone please explain simply what this means and how I could figure out for myself which has more character and which has larger/smaller lobes please?

Thanks

[FeLiXe]

in general bonding orbitals go toward the electronegative partner and antibonding orbitals to the less electronegative atom. the reason is that an electronegative atom attracts electrons stronger
in CO this means: the bonding HOMO, which could donate, has O character. the antibonding LUMO has C character.

[redfox]

Aah, put so simply:) Thanks,  appreciate it!