Valence electronIn chemistry and physics, a valence electron is an electron in the outer shell associated with an atom, and that can participate in the formation of a chemical bond if the outer shell is not closed. In a single covalent bond, a shared pair forms with both atoms in the bond each contributing one valence electron. The presence of valence electrons can determine the element's chemical properties, such as its valence—whether it may bond with other elements and, if so, how readily and with how many.
Doom metalDoom metal is an extreme subgenre of heavy metal music that typically uses slower tempos, low-tuned guitars and a much "thicker" or "heavier" sound than other heavy metal genres. Both the music and the lyrics are intended to evoke a sense of despair, dread, and impending doom. The genre is strongly influenced by the early work of Black Sabbath, who formed a prototype for doom metal.
Thrash metalThrash metal (or simply thrash) is an extreme subgenre of heavy metal music characterized by its overall aggression and often fast tempo. The songs usually use fast percussive beats and low-register guitar riffs, overlaid with shredding-style lead guitar work. The lyrical subject matter often includes criticism of The Establishment, opposition to armed conflicts, and at times shares a disdain for the Christian religion with that of black metal. The language is typically direct and denunciatory, an approach borrowed from hardcore punk.
Natural bond orbitalIn quantum chemistry, a natural bond orbital or NBO is a calculated bonding orbital with maximum electron density. The NBOs are one of a sequence of natural localized orbital sets that include "natural atomic orbitals" (NAO), "natural hybrid orbitals" (NHO), "natural bonding orbitals" (NBO) and "natural (semi-)localized molecular orbitals" (NLMO). These natural localized sets are intermediate between basis atomic orbitals (AO) and molecular orbitals (MO): Atomic orbital → NAO → NHO → NBO → NLMO → Molecular orbital Natural (localized) orbitals are used in computational chemistry to calculate the distribution of electron density in atoms and in bonds between atoms.
Auger effectThe Auger effect or Auger−Meitner effect is a physical phenomenon in which the filling of an inner-shell vacancy of an atom is accompanied by the emission of an electron from the same atom. When a core electron is removed, leaving a vacancy, an electron from a higher energy level may fall into the vacancy, resulting in a release of energy. Although most often this energy is released in the form of an emitted photon, the energy can also be transferred to another electron, which is ejected from the atom; this second ejected electron is called an Auger electron.
