Energy released through Chemical Reactions
Fission reaction: has to do with the splitting of atomic nuclei into two or more parts after crashing with a free neutron. Uranium is the only natural element that can easily be split. The small particles that travel at a incredible speed and crach with other uranium nuclei causing them to split is the particles of the nuclei that split. This leads to a chain reaction creating heat from the kinetic energy of the quickly moving particles. This heat is used to convert water to steam which then turns a turbine that turns a generator and creates electricity.
Nuclear fission diagram
(2009, Nuclear Chemistry)
The process in which hydrogen atoms fuse to form helium atoms is nuclear fusion. The pros to this are that this process produces the same amount of energy: kilogram for kilogram, as the best modern energy source which is nuclear fission. It also does not produce dangerous radioactive waste only helium. 
(2009, Nuclear Chemistry)
Disadvantages of nuclear fusion is that it isquite difficult to get a self-sustaining fusion reaction started. Because you have to heat the hydrogen up to extreme temperatures. Most of the time it takes more energy to do this than the energy that is produced in the reaction.
When fission or fusion appears the process of changing elementary particles from one type of particle to another type is not exactly perfect at all. If you measured the mass of the particles after fusion or fission took place, the mass would be less then it was before.
average fusion reactions and the energy discharge are given in the table below
D + D = H3+N=3.27 MeV
D + D = T + p = 4.04 MeV
T + D = He4 + n = 17.26 MeV
He3 + D = He4 + p = 18.34 MeV
Li6 + D = 2He4 = 22.4 MeV
Li7 + p = 2He4 = 17.3 MeV
He3 + He3 = 2p + He4 = 12.86 MeV
He3 + D = He4 + p = 18.34 MeV
Li6 + D = 2He4 = 22.4 MeV
Li7 + p = 2He4 = 17.3 MeV
He3 + He3 = 2p + He4 = 12.86 MeV
for some people its easier to understand the famous equation
E=mc2
(2009, Nuclear Chemistry)
