Question

How to determine frontier orbital size of an atom?

Answer 1

Explanation:

FMO theory The FMO theory was proposed by Kenichi Fukui in 1952. The prediction of pericyclic reaction is based on the interaction between frontier molecular orbitals (FMOs). ... Their concept is based on the assumption that orbital symmetry is conserved during a pericyclic reaction

Answer 2

The size of an atom is determined by its radius. The atomic radius of an isolated atom is the distance between the nucleus of an atom and it's outermost orbit.