BECE Science 2011 Paper

The superscript represents the mass number which is made up of neutrons and protonsThe value of the superscript is 25 .Number of protons + Number of neutrons $=25$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 $=12$Atomic number $=$ Number of electronsNumber of electrons $=$ Number of protonsNumber of electrons $=12$Number of protons $=12$Protons + Neutrons $=25$$12+$ Neutrons $=25$Neutrons $=25-12$Neutrons $=13$13 neutrons and 12 protons