I'm currently studying physics at A-level, and for particle physics I'm fine about the theory of the equations, I remember what equations to use etc, but I can't seem to get the right answers from my calculator. For example, when working out the specific charge of a carbon ion with Z = 6, A = 13 and a charge of 2+, the necessary equation would be Specific Charge = charge/mass. Which is: 2 x 1.60 x 10^-19 / 6 x 1.67 x 10^-27 + 7 x 1.67 x 10^-27 + 4 x 9.11 x 10^-31 When shortened is: 2 x 1.60 x 10^-19 / 13 x 1.67 x 10^-27 Which finally should = 1.47 x10^7 C kg^-1 But when I enter 2 x 1.60 x 10^-19 / 13 x 1.67 x 10^-27 into my calculator, I get a vastly different answer of 4.110769231 x 10^-47 Is there something I'm doing wrong? We haven't done particle physics in a while and I might be missing a vital step. Any help will be greatly appreciated.