Okay, the user wants me to translate "electron-shells" into Thai. Let me check if the term is already in Thai. No, it's in English. So I need to translate it. The correct translation for "electron shells" in Thai is "เปลือกอิเล็กตรอน". I should make sure there's no existing Thai content here. Since the input is English, I proceed with the translation. Just output the Thai term without any explanations.