The superscript represents the mass number which is made up of neutrons and protons The value of the superscript is 12 . Number of protons + Number of neutrons =12 The subscript represents the atomic number which is the number of electrons in a neutral atom. In a neutral atom, the number of electrons is equal to the number of protons. Atomic number =6 Atomic number = Number of electrons Number of electrons = Number of protons Number of electrons =6 Number of protons =6 Protons + Neutrons =12 6+ Neutrons =12 Neutrons =12−6 Neutrons =6