Iodine 131 and iodine 126 are the same in the sense that, they both have the same number of electrons and protons in their atoms, it is only the number of their neutrons that is different. Iodine 131 has 78 neutrons while iodine 126 has 73 neutrons.
To convert a cup measurement to a gallon measurement, divide the volume by the conversion ratio. The volume in gallons is equal to the cups divided by 16.
