Most of the heavy elements in the universe today originated from the explosive burning of super giant stars.
This graphic shows how nuclear material is burned to form heavy elements in a red-giant star such as Betelgeuse near the end of its life.
The process of a star exploding is called a super nova. Elements heavier than Iron appear to have been produced by the explosion of super giant stars early in the life of the universe.
With each generation of exploding stars and formation of new stars, the “metalicity” or metal content of the stars increase. The Horsehead nebula is a region in the Milky Way where new stars are being formed from the remnants of exploded stars.
This nuclear burning process results in many elements which have an imbalance of nucleons ie too many neutrons. These unstable elements decay into more stable states forming all the other elements in the periodic table.
In this lesson, we’ll study nuclear decay and the 3 major kinds of nuclear radiation.
To start with the He nucleus is the most stable of all nuclear building blocks. He has 2 protons and 2 neutrons.
When an unstable nucleus decays by losing a He nucleus it is called Alpha Decay. Alpha decay lowers the atomic number of the parent nucleus by 2 (protons) and lowers the atomic mass by 4 amu (2 protons + 2 neutrons).
Another way that a nucleus can get rid of excess neutrons when a neutron loses a high energy electron and transforms into a proton. This process is called Beta Decay.
The third method of nuclear decay happens when a high energy photon or light particle is emitted. This is called Gamma decay. In Gamma decay, the nucleus loses a large amount of energy. This usually happens when a nucleus splits into two or more parts such as during Alpha Decay.