It is our responsibility and our honor to use our platform to amplify the voices of the oppressed and marginalized. The Electron community believes that Black Lives Matter. Atomic theory is a scientific description of the nature of atoms and matter that combines elements of physics, chemistry, and mathematics. According to modern theory, matter is made of tiny particles called atoms, which are in turn made up of subatomic particles.Atoms of a given element are identical in many respects and different from atoms of other elements. Electron configuration was first conceived under the Bohr model of the atom, and it is still common to speak of shells and subshells despite the advances in understanding of the quantum-mechanical nature of electrons.. An electron shell is the set of allowed states that share the same principal quantum number, n (the number before the letter in the orbital label), that electrons may occupy. To be silent is to be complicit. Quantum field theory is the result of the combination of classical field theory, quantum mechanics, and special relativity. : xi A brief overview of these theoretical precursors is in order. Free-electron model of metals, in solid-state physics, representation of a metallic solid as a container filled with a gas composed of free electrons (i.e., those responsible for high electrical and thermal conductivity).