This book tries to lighten the difficulties of learners by focalizing in few areas of Physical Chemistry and approaching these areas with extensive and in-depth explanations combined with an easy-to-read style of presentation. This book deals only with quantum mechanics, atomic structure, thermodynamics, and symmetry because these are both at the basis of the whole Chemistry and are the topics requiring most attention.

· Formulas are extensively accompanied by clarifications of their roles and consequences followed by discussions and comments, prioritizing the explanation of the line of thinking over the technicalities, but also preferring to address directly the most challenging points, rather than conceal them.

· The selection of very few topics allows following a colloquial style with a simple language, while using an in-depth treatment of the subjects.

· Some topics pertinent to Mathematics (linear spaces and matrices, two necessary tools for quantum mechanics and symmetry) are treated separately with a more extensive presentation in appendixes, avoiding formalization, but exploiting the analogy with the vectors of ordinary 3D space.

· Strong emphasis is given to the connections between different areas of Physical Chemistry, such as the laws of motion (mechanics), symmetry, and macroscopic behavior (thermodynamics).

Prospected readers are not only students of Physical Chemistry courses in the first years for a degree in Chemistry, but also more advanced students willing to strengthen their previous knowledge, i.e., graduate or PhD students in various areas of Chemistry or related fields such as Biotechnology, Materials Chemistry or Energy and Environmental Technologies.

This is a reference book for a deeper understanding of the most fundamental parts of Physical Chemistry. It has been written both for making the study of the beginner easier and helping the advanced learner to clarify the most critical points.