In this reaction, we have a hydroxide with a negative sign interacting with a sodium ion with a positive sign, and we form sodium hydroxide. So which one has the homo and which one has the lumo? So clearly, this is our base. Why? Well, because it has a pair of electrons that it can donate that it can use to grab another molecule, in this case, atom. So that means this pair of electrons, the orbital that is found in, must be the homo.