atoms. consider hydrogen. hydrogen consists of a central nucleus and it turns out they put that plus sign there, because it's positively charged and around that nucleus, forms a negatively charged particle called an electron. we're gonna be talking more about this when we talk about electricity. this hydrogen has a chemical symbol h. guess why? hydrogen, hydrogen, yeah, okay? and then we have numbers like this. these digits, this digit down here corresponds to the atomic number. that tells you the number of charges that are in the nucleus. that's one. and this digit corresponds to the atomic mass, over here atomic number and this one here atomic mass. an atomic mass refers to the number of particles in the nucleus. we call these particles nucleons, because sometimes you can have a neutral particle in there called a proton. and when you have that proton, this is still hydrogen, turns out that positive nucleus-- yes, lee? the neutral particle is a neutron. - what did i call it? - a proton. oh, did i call the neu

this is for a hydrogen atom, now. yes. let's supposed i have a helium atom. now, we got two protons. it turns out there's two neutrons here too. and you know what? you know what's gonna happen to this space over here? take one guess. everyone. everyone. this charge out here now sees two protons tugging on it. how many say, "it'll be pulled into a tighter orbit"? how many say, "no, no, no, it'll stay the same"? how many say, "no, it'll be pushed further away"? check your neighbor. -- how many say it's gonna be tighter? yay, that's right. and it turns out, for a helium atom, the helium will hold the electron tight. and furthermore, it will hold another one too. the fact it holds another one makes it a little bit bigger, okay, 'cause they're repelling over here. but a helium atom is smaller. it turns out a helium atom won't gang up with any other atom, so there's no such thing as a helium molecule. we have two positive charges right next to each other like that, how do you deal with that? why don't those two positive charges repel? why don't they repel? look how

freter: when obsidian is first broken, it has a clean edge that absorbs hydrogen atoms from water atnown rate. it's the same kind of thing as if a piece of hard candy is left out. it will start to absorb a little bit of water and get softer and softer, while the center can still stay hard. obsidian is basically doing the same thing. and the longer that it's exposed to the elements, the thicker the hydration rim actually gets. and you can measure it and figure out a date. keach: the hydration layer is not visible to the naked eye, so a tiny section of the obsidian blade is magnified. freter: what you're looking at is the hydration layer, which runs right across the very edge of the obsidian, where the hydrogen atoms have gone into the piece of obsidian. and it goes from this black line right here down to that black line right there, and it runs all the way across the entire piece of obsidian. and it's that line that you actually measure. keach: although the technique is simple, it's time-consuming. and right from the beginning, freter ran into problems with her dates. the copan valley

the complex then splits to give the products-- a molecule of hydrogen bromide and a hydrogen atom. collision theory helps chemists understand how chemical reactions occur, even the most dramatic ones. but not all collisions result in a reaction. the colliding hydrogen and oxygen molecules in this balloon will not react unless you give them some additional energy. a far more dramatic hydrogen explosion took place on may 6, 1937, over new jersey. the world's largest hydrogen blimp, the hindenburg, was preparing to land after another safe atlantic crossing, but an accidental spark provided the additional energy for a terrifying reaction. there was a terrific explosion aft. brilliant orange flames formed a backdrop for a tableau of death. the hindenburg's 7 million cubic feet of hydrogen gas had ignited. the ship's tail plummeted to the ground. now, why did the hydrogen-oxygen reaction require additional energy, that extra push in order to get the reaction to go? well, the reasoning is that every chemical reaction requires an activation energy. now, activation energy is the minimum amou

safely nuclear fusion on the other hand is nature's atomic power just have to look at the some of the stars to see it in action in this reaction hydrogen isotopes in this case tritium and uteri and confined to form a heavy isotope helium a single neutron and lots of energy because most importantly the fusion gives off hardly any radioactive waste. a slow the idea of eater was first discussed at an international forum in washington in one nine hundred seventy five together with the leader of the us thermo nuclear program we gave a report on things we could do together and on ways to do them back in one nine hundred seventy five we said we should work on what is known today as a technological platform this was it or this is what we said back in one nine hundred seventy five and all the work after the basically followed this plan. of suggests that general secretary got about twelve bring it up at the geneva superpower summit in one thousand nine hundred eighty five he discussed it with president reagan and the international thermonuclear experimental reactor project was born in europe france in particular was already looking to diversify

safely nuclear fusion on the other hand is nature's atomic power just have to look at the some of the stars to see it in action in this reaction hydrogen isotopes in this case tritium and uteri and combined to form a heavy isotope helium a single neutron and lots of energy because most importantly fusion gives off hardly any radioactive waste. a slow the idea of eater was first discussed at an international forum in washington in one nine hundred seventy five together with the leader of the us thermo nuclear program we gave a report on things we could do together and on ways to do that back in one nine hundred seventy five we said we should work on what is known today as a technological platform this. this is what we said back in nine hundred seventy five and all the work after that basically followed this plan. of suggests that general secretary got about twelve bring it up at the geneva superpower summit in one thousand nine hundred eighty five he discussed it with president reagan and the international experimental react to project was ball in europe france in particular was already looking to diversify its energy sources and join t

safely nuclear fusion on the other hand is nature's atomic power just have to look at the some of the stars to see it in action in this reaction hydrogen isotopes in this case terri and combined to form a heavy isotope helium a single neutron and lots of energy because most importantly the fusion gives off hardly any radioactive waste. the idea of eater was first discussed at an international forum in washington in one nine hundred seventy five together with the leader of the us thermo nuclear program we gave a report on things we could do together.

safely nuclear fusion on the other hand is nature's atomic power you just have to look at the some of the stars to see it in action in this reaction hydrogen isotopes in this district here you combine to form a heavy isotope helium a single neutron and lots of energy because most importantly the fusion gives off hardly any radioactive waste. a slow the idea of eater was first discussed at an international forum in washington in one nine hundred seventy five together with the leader of the us thermo nuclear program we gave a report on things we could do together and on ways to do them back in one nine hundred seventy five we said we should work on what is known today as a technological platform this was it or this is what we said back in one nine hundred seventy five and all the work after that basically followed this plan which you. really have suggests that general secretary got about twelve bring it up at the geneva superpower summit in one thousand nine hundred eighty five he discussed it with president reagan and the international thermonuclear experimental reactor project was born in europe france in particular was already looking to

hydrogen peroxide. god, you're so smart. how about this one? qm2? i'm not sure what that is. it's quag-megium. it's the strongest compound on earth. nothing can separate it. it has an atomictie patootie. if i'm a cutie patootie, then you're a peenie-vageenie. aww! i heard a cute "aw" in there. cool down! meg, there's something we need to talk about. dad, i swear to god, i thought you could flush those things. meg, you ever heard of joan van ark? no. here's a picture of joan van ark. oh, my god, she's gorgeous. gorgeous. yes. yes, meg, gorgeous. yes. every man wanted her. but one man got her. a man she trusted to keep her safe and beautiful forever. that man was glenn quagmire. and two short months later, this is what happened to joan van ark. oh! oh, my god! i don't want this to happen to you, meg. i don't want you to turn into a hilarious photograph. dad, i know what you're trying to do, and i want you to stop it. mom! what is it, meg? mom, tell dad to leave me alone. i'm 18, and he keeps treating me like a kid. peter, i told you not to push her about this quagmire thing. if you push too hard, you're going to push her right into his arms. well, what am i supposed to do?