http://en.wikipedia.org/wiki/Photon
Quantum For example, a photon is a single quantum of light (or of any other form of electromagnetic radiation). Similarly, the energy of an electron bound within an atom is quantized and can exist only in certain discrete values. (Indeed, atoms and matter in general are stable because electrons can exist only at discrete energy levels within an atom.) Laser Device which emits light via optical amplification Red (660 & 635 nm), green (532 & 520 nm) and blue-violet (445 & 405 nm) lasers A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation.
Semiconductor Semi-conductive devices can display a range of useful properties such as passing current more easily in one direction than the other, showing variable resistance, and sensitivity to light or heat. Because the electrical properties of a semiconductor material can be modified by doping, or by the application of electrical fields or light, devices made from semiconductors can be used for amplification, switching, and energy conversion. The conductivity of silicon is increased by adding a small amount of pentavalent (antimony, phosphorus, or arsenic) or trivalent (boron, gallium, indium) atoms (part in 108).
Introduction to quantum mechanics Many aspects of quantum mechanics are counterintuitive[3] and can seem paradoxical, because they describe behavior quite different from that seen at larger length scales. In the words of quantum physicist Richard Feynman, quantum mechanics deals with "nature as She is – absurd".[4] For example, the uncertainty principle of quantum mechanics means that the more closely one pins down one measurement (such as the position of a particle), the less accurate another measurement pertaining to the same particle (such as its momentum) must become. The first quantum theory: Max Planck and black-body radiation[edit]
Relative atomic mass Relative atomic mass (symbol: Ar) or atomic weight is a dimensionless physical quantity defined as the ratio of the average mass of atoms of a chemical element in a given sample to one unified atomic mass unit. The unified atomic mass unit (symbol: u or Da) is defined as being 1⁄12 of the atomic mass of a carbon-12 atom.[1][2] Since both values in the ratio are expressed in the same unit (u), the resulting value is dimensionless; hence the value is said to be relative. For a single given sample, the relative atomic mass of a given element is the weighted arithmetic mean of the masses of the individual atoms (including their isotopes) that are present in the sample. This quantity can vary substantially between samples because the sample's origin (and therefore its radioactive history or diffusion history) may have produced unique combinations of isotopic abundances. Definition[edit]
Valence (chemistry) Valence only describes connectivity; it does not describe the geometry of molecular compounds, or what are now known to be ionic compounds or giant covalent structures. A line between atoms does not represent a pair of electrons as it does in Lewis diagrams. The maximum number of univalent atoms (originally hydrogen or chlorine atoms) that may combine with an atom of the element under consideration, or with a fragment, or for which an atom of this element can be substituted. The number of hydrogen atoms that can combine with an element in a binary hydride or twice the number of oxygen atoms combining with an element in its oxide or oxides. This definition differs from the IUPAC definition as an element can be said to have more than one valence. Most 19th-century chemists defined the valence of an element as the number of its bonds without distinguishing different types of valence or of bond.
Configuration state function In quantum chemistry, a configuration state function (CSF), is a symmetry-adapted linear combination of Slater determinants. A CSF must not be confused with a configuration. In general, one configuration gives rise to several CSFs; all have the same total quantum numbers for spin and spatial parts but differ in their intermediate couplings.
Slater determinant In quantum mechanics, a Slater determinant is an expression that describes the wave function of a multi-fermionic system that satisfies anti-symmetry requirements, and consequently the Pauli principle, by changing sign upon exchange of two electrons (or other fermions).[1] It is named for John C. Slater, who introduced the determinant in 1929 as a means of ensuring the antisymmetry of a wave function,[2] although the wave function in the determinant form first appeared independently in Heisenberg's [3] and Dirac's [4] papers three years earlier. The Slater determinant arises from the consideration of a wave function for a collection of electrons, each with a wave function known as the spin-orbital,
Electron configuration In atomic physics and quantum chemistry, the electron configuration is the distribution of electrons of an atom or molecule (or other physical structure) in atomic or molecular orbitals.[1] For example, the electron configuration of the neon atom is 1s2 2s2 2p6, using the notation explained below. Electronic configurations describe each electron as moving independently in an orbital, in an average field created by all other orbitals. Mathematically, configurations are described by Slater determinants or configuration state functions. According to the laws of quantum mechanics, for systems with only one electron, an energy is associated with each electron configuration and, upon certain conditions, electrons are able to move from one configuration to another by the emission or absorption of a quantum of energy, in the form of a photon.
Neon chemical element with atomic number 10 Neon is a chemical element with symbol Ne and atomic number 10. It is a noble gas.[10] Neon is a colorless, odorless, inert monatomic gas under standard conditions, with about two-thirds the density of air. It was discovered (along with krypton and xenon) in 1898 as one of the three residual rare inert elements remaining in dry air, after nitrogen, oxygen, argon and carbon dioxide were removed. Neon was the second of these three rare gases to be discovered and was immediately recognized as a new element from its bright red emission spectrum. The name neon is derived from the Greek word, νέον, neuter singular form of νέος (neos), meaning new.
Molecular orbital Complete acetylene (H–C≡C–H) molecular orbital set. The left column shows MO's which are occupied in the ground state, with the lowest-energy orbital at the top. The white and grey line visible in some MO's is the molecular axis passing through the nuclei.