[laze]

Hey I just had some questions regarding the HOMO/LUMO concept.

1) The idea of HOMO/LUMO deal with molecular orbitals, meaning this concept is only applied
to molecules with covalent bonds and not ionic, is this correct?

2) I recall reading somewhere that the gap between the HOMO/LUMO is what gives a compound its color,
the smaller the gap means it doesn't absorb visible light and as the gap increases then we notice a color for
the compound.

When we use bleach on something, it lowers the HOMO/LUMO gap of a compound and doesn't actually remove anything.

I don't remember where i read this, how accurate is what i recalled? What am i forgetting?

thank you!

[Schrödinger]

1) Pretty much, but not 100% covalency. MO theory does indeed allow for mixing of orbitals, which implies covalency

2) The HOMO-LUMO gap sometimes does impart colour, but your statement that as the gap increases we notice a colour is not exactly true. If the energy gap corresponds to the visible light wavelength region, it is only then we observe a colour. Increase/decrease of gap is only relative to this.

[laze]

Ah thank you very much!