Okay, the user wants me to translate "electron-shells" into Japanese. Let me think about the correct term here. "Electron shells" refers to the energy levels or layers in an atom where electrons reside. In Japanese, this is commonly translated as "電子殻" (denshi kaku). I should confirm if there's a more standard term, but I'm pretty sure "電子殻" is the right one. Since the original content isn't in Japanese, I need to provide the translation without any extra explanations. Just the term itself. Alright, that should do it.