I am trying to come up with an example to illustrate how E=mc2 applies to nuclear fission. I need to be sure to distinguish between mass and mass number. I feel like I have some thing on the brink of my mind and then I loose it. I guess I need some help as I am tired and don’t know how much longer I will be able to think! Any suggestions or sites (besides my ever faithful google:) I can visit would be great.