I'm working all alone with nobody to help me, and now i'm stuck! :( I'd really appreciate it if you could help me out. I'm working with the ground state of the one electron hydrogen atom. Trying to determine the radial dependence on probability density. It should only depend on the radial coordinate and not on the other spherical coordinates. I've got one book saying the the radial dependence of probability density is: [tex]P(r)dr = |\psi|^2 4 \pi r^2 dr[/tex] Now another says something along the lines of: I got these two from: http://phy.asu.edu/phy361-alarcon/FALL06/lecture22_1109.ppt (power point) and https://www.physicsforums.com/showthread.php?t=49807 Now why aren't they the same? Please help.