Nuclear physics  deals with the  nucleus of the atom and the neutrons and protons within it. It also deals with how these particles interact with each as well as external influences. The nucleus of an atom is a relatively small dense positively charged mass at the atom’s center consisting of two types of particles. These particles are the positively charged protons and neutrally charged neutrons that are bound together in the nucleus by way of the residual strong nuclear force between these particles.

The simplest atomic nucleus is that of hydrogen-1 and it is made of a single photon with no neutrons.		Other atomic nuclei are more complicate including helium-4 which consists of two photons and two neurons.

The nucleus is the densest part of the atom. Now the element of each atom is determined by the number of protons in the nucleus. The number of protons in the nucleus of an atom is called the atomic number (Z) and it is unique to each element, while it is the number of neutrons that determin isotopes of an element.

Each isotope has its own unique properties. The particle number is the total number of protons and neutrons in the nucleus as contrast to the atomic number which is unique to the element is number of protons in the nucleus. The atomic weight is the mass of the isotope in atomic mass units. The half-life of an isotope the time is takes half of a radiometric isotope to decay with stable isotopes having an infinite half-life.