ABSTRACT
Niels Bohr, in his atom model proposed in 1913, introduced the concept of quantization (or discreteness of matter at submicroscopic level), to derive the discrete energy levels of the hydrogen atom. In an atom, the atomic shells are divided into subshells and the subshells are further divided into orbitals. The nucleus was discovered by Ernest Rutherford in 1911, from the concentrated scattering of alpha particles by a central core of the atom, which was named the nucleus. A nuclide of an element can have different number of neutrons, known as the isotopes of the element. Another important concept of importance is the binding energy (BE). The fundamental difference between the electronic and nuclear energy levels is that the electronic energy levels are in the eV to keV energy range while the nuclear energy levels are in the MeV range due to the stronger nuclear binding. Radioactivity was discovered by Becquerel while studying the properties of a uranium compound.
