The origins of atomic physics were entwined with the development ofquantum mechanics itself ever since the first model of the hydrogenatom by Bohr. This introductory book aims to provide a gentle yet rigorous first course on atomic and molecular physics. The early atomic models to describe the atomic nuclei were explained, black body radiations laws were also explained, hydrogen atomic spectra were explained and discussed with details. The wave-particle duality concepts also re-visited and explained with more details. The hydrogen atomic spectra and their derivation from Bohr atomic model discussed and explained in more details.The discovery of x-rays and their spectroscopy is carefully explained. The special theory of relativity are carefully treated and explained. The basic concepts for molecules also included in this book.