so they call this neptunium. first element beyond uranium and that's neptunium 239. it's got a very, very short half-life. and you know what it does? it decays. and guess what it emits? begins with a b. no, not alpha. try it again. it emits a beta particle. okay. it emits a beta particle. and what does it turn into? how many people can figure out what the number is here that couldn't do it before but maybe now can? show of hands. four people. wonderful. now, how many? what is it gonna be, gang? it's 94. 94, 94. what is the second planet that we named after discovering by newton's laws? it wasn't neptune, it was what? - pluto. - pluto. guess what we'd be calling this, gang? plutonium. plutonium. pu239. and you know what plutonium will do? plutonium as well as uranium 235 will undergo fission when a neutron taps it. and so this is used for power production. u235, used for power production. historically, when the bombs were dropped back in world war ii, the bomb that devastated hiroshima was a uranium 235 bomb. you know how much uranium 235 was left after the bomb was d