Dear Pooja

All electron shells represent an energy level - it doesn't matter if its the outermost shell or not.
In order for there to be a release of energy the electron has to be coming from a higher energy state. The only energy state higher than the outer-most electron shell would be a free electron.
The only way an electron becomes a free electron is that sufficient was provided to lift it from what-ever electron shell (energy level) it was previously in to escape velocity. The energy that it then releases in returning is then this exact same amount of energy.

All the best.                                                           

AKASH GOYAL

AskiitiansExpert-IIT Delhi

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