The field of physics which studies atoms as an atomic nucleus and an isolated system of electrons is known as atomic physics. Its fundamental concern is the arrangement of electrons around the nucleus and the mechanisms through which these arrangements change. Both neutral atoms and ions are studied under this discipline. The processes of ionization and excitation by photons or collisions with atomic particles are also dealt within this field. The underlying theory in plasma physics and atmospheric physics has been provided by atomic physics. This book discusses the fundamentals as well as modern approaches of atomic physics. Coherent flow of topics, student-friendly language and extensive use of examples make it an invaluable source of knowledge. This book is an essential guide for both academicians and those who wish to pursue this discipline further.