Why does splitting an atom create energy? And why is it so much energy?
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Atoms are made up of Protons, Neutrons and electrons. We can individually ‘weigh’ protons and neutrons to work out their mass (electrons are very low mass, so lets ignore them)
if you jam a bunch of protons and neutrons together to form an atom (lets say uranium 235, that has 92 protons and 143 neutrons, so a big heavy atom)
What should the atom weigh? 92 x proton weight + 143 x neutron weight right? its what you would expect, but it doesn’t, it weights less than this.
This mass difference is made up of the ‘nuclear binding energy’ (yeh, mass converting to energy and back, there is complicated science here too)
So now we crack that atom like a walnut, into two smaller atoms. Now weigh these, surely the total mass will be same the same as the original right? you would think, but the total mass is now a little Higher.
This is now where E=MC squared comes in (its actually change in energy = change in mass times the square of the speed of light) and because of the change in mass, there is a change of energy, and the excess energy gets released as heat/motion, usually through the reaction kicking out a seriously fast moving neutron or similar.
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