The superscript represents the mass number which is made up of neutrons and protons The value of the superscript is 27 . Number of protons + Number of neutrons =27 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 =13 Atomic number = Number of electrons Number of electrons = Number of protons Number of electrons =13 Number of protons =13 Protons + Neutrons =27 13+ Neutrons =27 Neutrons =27−13 Neutrons =14