The helium nucleus is constantly colliding with the walls of the nucleus and due to its mass and energy it will tunnel out of the nucleus. Alpha reaction Beta decay occurs when there are too many neutrons compared to protons, which makes the nucleus unstable. In basic beta decay the neutron is turned into a proton and an electron, the electron is then emitted. The resulting element will have one more proton than the original element. Beta reaction Beta decay also happens when the neutron to proton ratio is too small, this happens by positron emission.
In this beta decay a proton is turned into a neutron and a positron, the positron is then emitted from the nucleus. When the proton to neutron ratio is too small there can also beta decay by electron capture where an electron is captured by the nucleus and turns a proton into a neutron. Nuclear Fission reactions differ from natural radioactive decay both in how the reactions are started and also the products that are formed. Radioactive decay happens when the nucleus is unstable due to the number of protons and neutrons within the nucleus.
The nucleus is made stable by the emission of particles from the decaying nucleus. In nuclear fission a neutron is fired at an atoms nucleus, if the neutron has given the atom enough energy it will enter an excited state and begin to oscillate. When these oscillations become unstable the nucleus will split into two smaller nuclei which are similar in mass, more neutrons are emitted and these neutrons can cause further fission to surrounding nuclei.
The chain reaction which can be caused by nuclear fission makes the products from the reaction different to that of natural radioactive decay. In natural radioactive decay there are two products formed, in alpha decay a helium atom and also another atom with two less protons and neutrons will be formed and in beta decay an electron and an element with one more proton than the original element will be formed. In nuclear fission reactions the products formed are two atoms of similar masses and when a chain reaction is created there can be many products formed from the reaction.
Nuclear fission reaction Chain reaction Hydrogen and helium nuclei are simple elements in which heavier elements are made from. These heavier elements are made from the simple chemical elements by different processes which collectively are called nucleogenesis. In the sun hydrogen is converted into helium by nuclear fusion reactions Hydrogen to He reaction As stars evolve hydrogen is used to make more helium atoms which is then used in a series of fusion reactions.
Helium nuclei react to form beryllium, oxygen, carbon, magnesium and neon and in the following reactions: Reactions All of the reactions give out energy which reaches the earth as heat and light. There are two ways in which lithium forms in stars. The first involves the fusing of helium nuclei with tritium which is an isotope of hydrogen. The second involves helium-4 and helium-3 colliding with a Beryllium atom and an electron causing a change in the nucleus and the formation of 7Be. The proton number decreases by 1 and the structure is altered.