[Asma]

1) what is the order of difference of HOMO to LUMO in halogens?
where HALO is : highest occupied molecular orbital and
LUMO is : Lowest Unoccupied molecular orbital.

2) In which molecule homo to lumo distance is highest?

thanks

[ARGOS++]

Dear Asma,

The order is ALL times the same, also for Halogens!!

LUMO is all times the NEXT, HIGHER Orbital as the HOMO, that’s from where it got its name !!
You may search for a picture under the term: “Jablonsky Diagram” wherein the S₀ state is the so called HOMO state.
As the energy gap between HOMO & LUMO defines the wavelength of its Absorption, to get the excited state, you have to search for a colourless (UV/Vis) Atom/Molecule with the shortest possible wavelength of its first Absorption.

For a first Example I think about Quartz (SiO₂), which is at the same time also the best known insulator, what is an additional indication for what you are searching.

About the relation between wavelength and corresponding energy you may read the answer to:

Why Einstein meets Beer-lambert?

There you can also find a nice Energy-Wavelength-Diagram(for your printer, -only?).


Good Luck!
                    ARGOS⁺⁺