When an electron absorbs a photon, it gets into a higher energy state and goes into the upper orbit/shell.
Does (rather should) this absorption of energy also have an impact on its mass (although incredibly small)?
Can we even measure the mass of an electron while it is it still bound to the nucleus?
Answer
This is really an extended comment to Geoffrey's answer, so please upvote Geoffrey's answer rather than this.
The mass of a hydrogen atom is $1.67353270 \times 10^{-27}$ kg. If you add the masses of a proton and electron together then they come to $1.67353272 \times 10^{-27}$ kg. The difference is about 13.6eV, which is the ionisation energy of hydrogen (though note that the experimental error in the masses isn't much less than the difference so this is only approximate).
This shouldn't surprise you because you have to add energy (in the form of a 13.6eV photon) to dissociate a hydrogen atom into a free proton and electron, and this increases the mass in accordance with Einstein's famous equation $E = mc^2$. So this is a direct example of the sort of mass increase you describe.
However you can't say this is an increase of mass of the electron or the proton. It's an increase in mass of the combined system. The invariant masses of the electron and proton are constants and not affected by whether they're in atoms or roaming freely. The change in mass is coming from a change in the binding energy of the system.
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