'''INTRODUCTION''' This course is intended to introduce the students to concepts of theoretical chemistry and molecular modeling. A practical approach will be used guiding the student from the fundamental theoretical background to the practical aspects of the models: definition, analysis and interpretation. The topics and ideas presented in each section are reinforced with varied exercises, references, and further readings. ---- '''INTRODUCTION''' The contents of the course is structured as follows: # The molecular Hamiltonian and the solution of the Schroedinger equation. *a.- The HF approximation. Differential equation. *b.- The RHHF equations. The algebraic equation. # The BO approximation. Geometry Optimization. #- Molecular energy and the potential energy surface. #- Analysis of the WFN: Molecular properties. #- Molecular geometry. The concept of molecular structure.