Inside the nucleus there are: Protons Neutrons The nucleus is held together by the strong nucleus force. The nucleus is not always stable! The number of protons and neutrons can influence the stability of the nucleus. Usually a 1:1 ratio is stable. More than this is unstable Certain isotopes of elements are said to be unstable, and as a result they break down radioactive. All elements with an atomic number above 82 have at least one radioactive isotope. There are three major types of radioactivity: Composed of 2 protons and 2 neutrons A helium nucleus Made of a single negative charge Basically an electron High energy photon No mass Alpha particles lost: A nucleus loses 2 protons and 2 electrons This produces a loose alpha particle and an atom that is “lighter” with an atomic number lower by two and an atomic mass lower by 4 amus. Beta particles lost: A neutron is made up smaller particles In radioactive isotopes sometimes a neutron will spontaneously break apart, releasing a beta particle (electron). What remains is a proton The neutron breaks apart into a proton and an electron. The electron is released from the nucleus and the proton stays. Gamma Rays: The most penetrating and high energy type of radioactivity. Large amounts of photon energy is released The nucleus is unchanged in numbers of protons and neutrons, but becomes more stable. Alpha particles are the most heavy but least penetrating. Gamma rays are pure energy, have no mass, but are the most penetrating. 1. Fission: This occurs when a radioactive nucleus splits to form two smaller, more stable nuclei This can lead to dangerous chain reactions! A common source of Uranium-235 is used as a fuel in nuclear reactions. It undergoes a number of reactions to release a great deal of energy, which in a reactor is harvested and used for power. Another common source of fuel is Uranium-238 The end result of all of the reactions is a stable isotope of lead! 2. Fusion: This type of reaction involves two small nuclei coming together to form a larger nuclei. This is how the sun works Nuclear fusion produces an enormous amount of energy, more than fission. However the reaction is very unstable and dangerous. Can only be contained in stars like the sun.