Modern chemistry is built upon the foundations of quantum mechanics. This course aims to provide a solid understanding of the fundamental concepts and standard topics of quantum mechanics, while also emphasizing its applications in chemistry. To achieve this, key topics such as the harmonic oscillator, angular momentum, spin, and hydrogen-like atoms will be presented in conjunction with the fundamental principles and concepts of spectroscopy. This knowledge serves as a foundation for understanding chemical bonding, electronic states of molecules, and the quantum theory of chemical reactivity, which are covered in "Quantum Chemistry II."