1. The problem statement, all variables and given/known data I need to figure out the energy, rest mass, speed, wavelength and momentum of a 2.2 eV electron. Thats all it says. 2. Relevant equations Ek = 1/2mv^2 3. The attempt at a solution I dont understand what 2.2 eV is. The kinetic energy? This converts to 3.52x10^-19 J Rest mass should be 9.11x10^-31. Or do I use E=mc^2? Why or why not? No idea how to find speed, which I need to calculate wavelength and momentum. I could use Ek= 1/2mv^2 because the electron will not be travelling close to the speed of light, but I feel like this is not the way you SHOULD calculate it. There has to be another way.