Science / Chemistry Glossary

Effusion: Gas molecules in a container escape from tiny pinholes into a vacuum with the same average velocity they have inside the container. They also move in straight-line trajectories through the pinhole.

Electric Charge: A property used to explain attractions and repulsions between certain objects. Two types of charge are possible: negative and positive. Objects with different charge attract; objects with th . . . View Full Definition

Electric Current: A flow of electric charges. The SI unit of electric current is the ampere.

Electric Dipole: An object whose centers of positive and negative charge do not coincide. For example, a hydrogen chloride (hcl) molecule is an electric dipole because bonding electrons are on average closer . . . View Full Definition

Electric Dipole Moment: A measure of the degree of polarity of a polar molecule. Dipole moment is a vector with magnitude equal to charge separation times the distance between the centers of positive and negative c . . . View Full Definition

Electric Field: A field of forces that act on any electric charge placed within it. The stronger the field, the stronger the force that acts on the charge. For example, the positive charge on an atomic nucl . . . View Full Definition

Electrical Conductivity: A measure of how easily an electric current can pass through a material. The conductivity is the reciprocal of the resistance. The SI unit of conductance is the siemens.

Electrical Resistance: The ability of a material to oppose the flow of an electric current, converting electrical energy into heat. The SI unit of resistance is the ohm.

Electrochemical Cell: A device that uses a redox reaction to produce electricity, or a device that uses electricity to drive a redox reaction in the desired direction.

Electrode: An electrically conducting surface that allows electrons to be transferred between reactants in an electrochemical cell.

Electrolysis: The process of driving a redox reaction in the reverse direction by passage of an electric current through the reaction mixture.

Electrolyte: A substance that dissociates fully or partially into ions when dissolved in a solvent, producing a solution that conducts electricity. See strong electrolyte, weak electrolyte.

Electrolytic Cell: A device that uses electricity from an external source to drive a redox reaction.

Electromagnetic Radiation: A wave that involves perpendicular oscillations in the electric and magnetic fields, moving at a speed of 2.99792458×108 m/s in a vacuum away from the source. Gamma rays, x-rays, ultraviolet . . . View Full Definition

Electron: A fundamental consituent of matter, having a negative charge of 1.602 176 462 × 10-19 coulombs ± 0.000 000 063 × 10-19 coulombs and a mass of 9.109 381 88 × 10-31 kg ± 0.000 000 72 × 10-31 k . . . View Full Definition

Electron Affinity: The enthalpy change for the addition of one electron to an atom or ion in the gaseous state. For example, the electron affinity of hydrogen is deltah in the reaction H(g) + e- rightarrow H-( . . . View Full Definition

Electron Configuration: A list showing how many electrons are in each orbital or subshell. There are several notations. The subshell notation lists subshells in order of increasing energy, with the number of electr . . . View Full Definition

Electron Volt: Energy required to move an electron through a potential difference of 1 volt. An electron volt is equivalent to 1.6×10-19 J.

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