DDs science book today threw mom for a loop. It introduces the periodic table of elements but doesn't tell you how to find one of the items you are supposed to figure out. We think we figured it out but even with google, I couldn't find the answer. If DH were here, he'd know but he's gone until late tonight. I knew someone here would know. They want us to find the number of neutrons. Do you take the atomic mass and subtract all the #s on the right (# of electrons in each shell)?