An electrically charged chemical particle. "Anions" are negatively charged, and "cations" are positively charged.
molecule
The smallest physical unit of a substance that retains all the physical and chemical properties of that substance. It may consist of a single atom or of a group of atoms bonded together chemically.
Ohm's Law
The relation amongst the current flowing through a resistor and the potential difference between the two ends of the resistor. The potential difference is equal to the product of the current and the resistance (volt = ampere x ohm).
passivation
The formation of a thin adherent film or layer on the surface of a metal or mineral that acts as a protective coating to protect the underlying surface from further chemical reaction, such as corrosion, electrodissolution, or dissolution. The passive film is very often, though not always, an oxide. A passivated surface is often said to be in a "passive state". The surface oxidation can result from chemical or electrochemical (anodic) oxidation. During anodic passivation, using linear-sweep voltammetry, the current first increases with potential, then falls to a very small value.
pH
A measure of the acidity/alkalinity (basicity) of a solution. The pH scale extends from 0 to 14 (in aqueous solutions at room temperature). A pH value of 7 indicates a neutral (neither acidic nor basic) solution. A pH value of less than 7 indicates an acidic solution, the acidity increases with decreasing pH value. A pH value of more than 7 indicates a basic solution, the basicity or alkalinity increases with increasing pH value.
The pH of a solution is equal to the negative, ten-based logarithm of the activity of the hydrogen ions in the solution. Neutral water dissociates into equal amounts of hydrogen (H+) cations and hydroxyl (OH-) anions. As the product of the concentrations (activities) of the two ions is always a constant 10-14, water has a pH of 7. In acidic solutions the hydrogen ions are in excess, while in basic solutions the hydroxyl ions are in excess.
polarity
Indicates the sign of the potential of an electrode, that is, it can be negative or positive.
polarization
The change of potential of an electrode from its equilibrium potential upon the application of a current. Somewhat confusingly, the term "polarization" is often also used in place of overvoltage. In bioelectrochemistry: the separation and grouping of opposite electrical charges so that two clear groups are perceptible as two distinct poles. Similarly, the term in general means the separation and grouping of opposite electrical charges (across any material) so that two clear groups are perceptible as two distinct poles.
rectifier
An electrical equipment that converts alternating current into direct current.
resistivity (electrical)
The measure of a material's inability to carry electrical current. The measurement unit of the resistivity (resistance) is the ohm. See also impedance.
The reciprocal of conductivity.
surface tension
The work required to increase a surface area, for example, to increase the size of a drop of water. When two phases are involved, it is often called an "interfacial tension", for example, to increase the size of a mercury droplet under water.
throwing power
A qualitative term used in electroplating to describe the ability of the system to produce a uniformly thick deposit on the substrate surface. That is, the "throwing power" is considered "good" when the current distribution is uniform even on an irregularly shaped substrate.
volt
Measurement unit of the electrical potential. Symbol: "V". A term named in honor of Alessandro Volta,.
watt
Measurement unit of electrical power. Symbol: "W". Related units are that of power density: watt/kilogram (W/kg) and watt/liter (W/l).
