Alpha decay () is the emission of an alpha particle from an atom’s nucleus; it contains two protons and two neutrons – which is equivalent to a helium-4 nucleus. When an atom emits an particle, the atom's atomic mass will decrease by four (because two protons and two neutrons are lost) and the atomic number will decrease by two. An example of alpha decay takes place when uranium decays into thorium by emitting an alpha particle.
Beta decay (β) is the conversion of a neutron into a proton and an electron, where the electron is expelled from the atom as a β-particle. When this occurs the mass of the atom will not change, though the atomic number will increase by one, since there is an additional proton, an example of this is the decay carbon-14 into the nitrogen. Natural radioactive decay works according to the principle of half-life; this is the amount of time needed for one-half of the radioactive substance to decay. In contrast, nuclear fission is the splitting of an atoms’ nucleus into smaller parts, releasing a large amount of energy in the process. (The energy produced is from the direct conversion of matter into energy, according to Einstein’s equation E=mc2). This is usually done by firing a neutron at the atoms’ nucleus. The energy of the neutron makes the intended element to divide into free neutrons and two (or more) smaller nuclei.
Under the extremely high temperatures and pressures within the core of stars, atoms collide at high speeds that overcome the electromagnetic repulsion of nuclei, allowing nuclear fusion. In the initial step of the procedure, two hydrogen atoms fuse to create deuterium. Subsequently, another hydrogen atom fuses with the deuterium, creating an isotope of helium that has two protons and one neutron. In the final step, both the isotopes fuse to produce a normal helium atom and a normal hydrogen nucleus. Elements such as lithium are made from these two elements in a range of procedures called...
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