nothing it just means normal carbon atom,,,it has been mentioned as carbon has isotope which has molecular mass 14 which is used in carbondating to find life of plants bcoz it is an radioactive isotope,,,so its an normal carbon form
I guess there's a difference... when you say isotope, you are worried more about the nucleus and not too much abt the electronic config..... there need not be a ground stt config or even the 6 electrons in C 12 isotope....