Understanding Atom Excitation: Natural vs Triggered Movement and Photon Emission

[wavingerwin]

I understand that when a particular atom is shone by white light, some corresponding spectra of white light will be absorbed by the atom to excite its electrons.

My question is, when an atom has its electrons excited, does it "naturally" tend to bring back its electrons to the ground state (or lower state) and emits photons along the way, or do we have to "trigger" the movement? (the atom tends to conserve its electrons in excitement)

Thank you!

 

[nooma]

Electrons tend to want to be in the lowest possible energy state. When an electron has been given the extra energy and jumped up the shell levels to another energy level, this is an unstable state for it to be in. It will naturally fall back down to the lowest possible energy level, releasing the difference between the energies as a particular wave length of light.

You do not need to induce the movement of the electron back to the ground state.

 

[Bob S]

I understand that when a particular atom is shone by white light, some corresponding spectra of white light will be absorbed by the atom to excite its electrons.

This effect was demonstrated to us by my freshman chemistry professor. He darkened the classroom, put a dish of liquid mercury on a hotplate between a UV "black light" (which emits the UV mercury lines) and a fluorescent screen. We saw the shadow of mercury vapor coming off the dish of hot mercury, like the smoke coming off a lit cigarette. (this professor is now deceased)

 

[nooma]

haha... poor guy