In the symbol he, the superscript 4 is the for helium, and the subscript 2 is the for helium. all of the answers i've looked up have been wrong. i believe i've found the answer. look on page 293 of your textbooks. the textbook says,  "the common symbol for an alpha particle is 4/2 he. the subscript is the atomic number (the number of protons). the super- script is the mass number (the sum of the numbers of protons and neutrons)."therefore the answer should be: super-script 4 is the mass number, subscript  2 is the atomic number