Atom emitting more than one frequency at the same time

[granpa]

in a single atom can more than one electron be transitioning between electron shells at the same time? can the atom be emitting more than one frequency at the same time? or is there some rule against this?

 

[mgb_phys]

There can be multiple unrelated transitions in an atom.
At the same time depends on how accurately you want to measure - ultimately two events can't happen at the same time if you use small enough intervals of time.
(ie do you mean within a microsecond, nanosecond, femtosecond .etc of each other)

 

[granpa]

during the time that the atom is emitting (as light) the energy released by the transition.

 

[Redbelly98]

It's possible for an atom to emit two (or more) photons during a transition between energy levels. The photons have different wavelengths (in general), the requirement is the sum of their energies equals the transition energy.

If I remember correctly, hydrogen in the 2S excited state decays primarily by emitting 2 photons.