Quantum chemistry

The quantum theory has many mathematical approaches, but the philosophy is essentially the same. Quantum mechanics is the foundation of chemistry, because it deals with subatomic particles, as well as atoms, molecules, elements, compounds, and much larger systems.
At the sub-atomic scale, there is no boundary between particles and waves. In fact, both particles and wave properties must be considered simultaneously for a system. The study of quantum mechanics lead us to understand the material and the universe beyond the general perception of matter by our ordinary senses of tasting, seeing, hearing, feeling, and sensing.
Furthermore, when coupled with the theory of relativity developed by Einstein, there is no boundary between material and energy. Energy and mass are equivalent, and they can convert into each other.

Modules of Quantum Theory

• Electromagnetic Radiation
  Transmission of energy through space via no medium is electromagnetic radiation. The visible region of the electromagnetic radiation is light, but that is a very small region. There is much more than light to meet the eye.
• Spectra
  Diagrams showing the distribution of intensity versus wavelengths are called spectra. Their study reveals the fundamentals of electromagnetic radiation as well as leading to useful applications. For example, the Hydrogen Spectra study led Bohr and others to develop the quantum theory to describe the atomic structures. For some cool spectrum demonstration, check out the IR Tutor created by Charles Abrams. Here is one of his animated pictures.
• Quantum numbers
  The states of electrons are represented by wavefunctions. Each wavefunction has a set of numbers, called quantum numbers. We often use quantum numbers to describe properties of electrons. This page gives a simplistic but important view of quantum numbers.
• Atomic orbitals
  Electronic states, represented by wavefunctions, in an atom are called atomic orbitals. Since we use quantum numbers to describe them, atomic orbitals are labelled by quantum numbers, such as 2s orbital, s represent quantum number l = 0, that implies m = 0. Each atomic orbital accomodates two electrons due to electron spin.
• Periodic table
  The beauty of quantum theory is its mathematical results not only explain the arrangement of the elements in the Periodic Table of chemical elements, but they seem rationalize the existence of the elements. Its rationalization lies in the Electronic configuration of atoms with more than two electrons. Based on the electronic configurations, Atomic properties are nicely explained.