protons and neutrons bounce around inside a nucleus | |
probability that proton or neutron in any region | |
minuscule chance that 2 alpha particles together outside the nucleus greater chance in a large nucleus than in a small one | |
Outside range of strong force
like a suddenly released spring the positive alpha particle will be repelled from nucleus |
for heavy atoms, nucleus may - for shortest of instants - exist in a state that allows it to blow apart