Why doesn't a photon excite a mercury atom with energy equal to the excitation energy?

[LHC]

Let's say, for ease of reference, an electron strikes a mercury atom with just enough energy such that this mercury atom is excited to another energy level. What would happen if a photon struck this atom with the same amount of energy? I remember encourtering a True/False problem like this in a textbook, and the answer was that it won't be excited. How is this so?

 

[dynamicsolo]

It sounds like what the question intends is that the electron has a certain amount of kinetic energy, but only transferred a portion of it to an atomic electron to cause its upward "transition" (the colliding electron continues on with reduced KE). The photon's energy is being compared to the electron's initial kinetic energy, rather than the energy required for the transition. Anyway, that's how I'm understanding this.

I guess it isn't clear what is referred to in the question by the phrase "same amount of energy". The same as what?