ChemEd DL Glossary

Glossary extended from the original PTL!

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v
valence bond theory
The theory that describes covalent bonding in terms of the overlap of atomic orbitals on pairs of atomsThe smallest particle of an element that can be involved in chemical combination with another element; an atom consists of protons and neutrons in a tiny, very dense nucleus, surrounded by electrons, which occupy most of its volume.; each bond is localized between two atoms and usually consists of one or more electronA negatively charged, sub-atomic particle with charge of 1.602 x 10-19 coulombs and mass of9.109 x 1023 kilograms; electrons have both wave and particle properties; electrons occupy most of the volume of an atom but represent only a tiny fraction of an atom's mass. pairs.
valence electron
In a neutral atomThe smallest particle of an element that can be involved in chemical combination with another element; an atom consists of protons and neutrons in a tiny, very dense nucleus, surrounded by electrons, which occupy most of its volume., any of the electrons found in the highest occupied shell as well as any electrons in incompletely filled subshells of lower shells.
valence-shell electron-pair repulsion theory
A means of predicting the structures of simple ions and molecules, or of individual atomsThe smallest particle of an element that can be involved in chemical combination with another element; an atom consists of protons and neutrons in a tiny, very dense nucleus, surrounded by electrons, which occupy most of its volume. in more complexA central metal and the ligands surrounding it; also called coordination complex. molecules or ions, by counting the number of pairs of electrons in the valence shell of a central atomIn a small molecule or ion, the atom to which the other atoms are bonded. The central atom is surrounded by the other atoms..
van der Waals equation
An equation that describes the behavior of gases and takes into account the effects of non-ideal behavior such as the non-negligible size of molecules of gas and forces of attraction between the molecules.
van der Waals forces
Attractive forces between polarDescribes a molecule that has separated, equal positive and negative charges that consitute a positive and a negative pole; such a molecule tends to assume certain orientations more than others in an electric field. or non-polar molecules, but not including hydrogen bonding.
vapor
The gaseous state of a substanceA material that is either an element or that has a fixed ratio of elements in its chemical formula. that typically exists as a liquidA state of matter in which the atomic-scale particles remain close together but are able to change their positions so that the matter takes the shape of its container or solidA state of matter having a specific shape and volume and in which the particles do not readily change their relative positions.; a gas at a temperatureA physical property that indicates whether one object can transfer thermal energy to another object. near or below the boiling pointThe temperature at which the vapor pressure of a liquid equals the pressure of the gas in contact with the liquid; usually this is atmospheric pressure. of the corresponding liquid.
vapor pressure
The pressureForce per unit area; in gases arising from the force exerted by collisions of gas molecules with the wall of the container. (or partial pressureThat portion of the total pressure of a mixture of gases contributed by the presence of one of the component gases.) exerted by the gaseous form of a substanceA material that is either an element or that has a fixed ratio of elements in its chemical formula. in equilibriumA state in which no net change is occurring, that is, in which the concentrations of reactants and products remain constant; chemical equilibrium is characterized by forward and reverse reactions occurring at the same rate. with the liquidA state of matter in which the atomic-scale particles remain close together but are able to change their positions so that the matter takes the shape of its container form.
vaporization
The formation of a vaporThe gaseous state of a substance that typically exists as a liquid or solid; a gas at a temperature near or below the boiling point of the corresponding liquid. from a liquidA state of matter in which the atomic-scale particles remain close together but are able to change their positions so that the matter takes the shape of its container; evaporation or boilingThe process of a liquid becoming vapor in which bubbles of vapor form beneath the surface of the liquid; at the boiling temperature the vapor pressure of the liquid equals the pressure of the gas in contact with the liquid..
viscosity
The resistance of a liquidA state of matter in which the atomic-scale particles remain close together but are able to change their positions so that the matter takes the shape of its container to flow when subjected to shear stress.
voltaic cell
An electrochemical cellA system containing an oxidation-reduction reaction in which oxidation and reduction reactions are physically separated and the transferred electrons pass through an electrical circuit. Voltaic (galvanic) cells produce and electic current; electrolyic cells use electric current to force a reaction to occur. in which a spontaneousCapable of proceeding without an outside source of energy; refers to a reaction in which the products are thermodynamically favored (product-favored reaction). reaction occurs. Such a cell can be used to generate electricity. Also called Galvanic cellAn electrochemical cell in which a spontaneous reaction occurs. Such a cell can be used to generate electricity. Also called voltaic cell..
VSEPR theory
Abbreviation for valence-shell electron-pair repulsion theoryA means of predicting the structures of simple ions and molecules, or of individual atoms in more complex molecules or ions, by counting the number of pairs of electrons in the valence shell of a central atom.; a means of predicting the structures of simple ions and molecules, and single atomsThe smallest particle of an element that can be involved in chemical combination with another element; an atom consists of protons and neutrons in a tiny, very dense nucleus, surrounded by electrons, which occupy most of its volume. in more complexA central metal and the ligands surrounding it; also called coordination complex. molecules or ions, by counting the number of pairs of electrons in the valence shell of a central atomIn a small molecule or ion, the atom to which the other atoms are bonded. The central atom is surrounded by the other atoms..
vulcanization
A process for increasing the strength and hardness of rubberA tough, elastic polymer obtained from the juices of certain tropical plants; a synthetic material having similar properties. by heating the rubber in the presence of sulfur.