The debye (symbol: D) (; ) is a CGS unit (a non- SI

metric Metric or metrical may refer to: * Metric system, an internationally adopted decimal system of measurement * An adjective indicating relation to measurement in general, or a noun describing a specific type of measurement Mathematics In mathe ...

unit) of

electric dipole moment The electric dipole moment is a measure of the separation of positive and negative electrical charges within a system, that is, a measure of the system's overall polarity. The SI unit for electric dipole moment is the coulomb- meter (C⋅m). ...

Two equal and opposite charges separated by some distance constitute an electric dipole. This dipole possesses an

whose value is given as charge times length of separation, it is a vector whose direction is in the direction of the unit vector of the position vector of the positive charge w.r.t negative charge: :p = ''q''r. named in honour of the physicist

Peter J. W. Debye Peter Joseph William Debye (; ; March 24, 1884 – November 2, 1966) was a Dutch-American physicist and physical chemist, and Nobel laureate in Chemistry. Biography Early life Born Petrus Josephus Wilhelmus Debije in Maastricht, Netherlands, D ...

. It is defined as

statcoulomb The franklin (Fr) or statcoulomb (statC) electrostatic unit of charge (esu) is the physical unit for electrical charge used in the cgs-esu and Gaussian units. It is a derived unit given by : 1 statC = 1 dyn1/2⋅cm = 1 cm3/2⋅g1/2⋅s−1. Tha ...

centimeter 330px, Different lengths as in respect to the Electromagnetic spectrum, measured by the Metre and its deriveds scales. The Microwave are in-between 1 meter to 1 millimeter. A centimetre (international spelling) or centimeter (American spellin ...

s.The statcoulomb is also known as the franklin or electrostatic unit of charge. :1 statC = 1 Fr = 1 esu = 1 cm^3/2⋅g^1/2⋅s⁻¹. Historically the debye was defined as the dipole moment resulting from two charges of opposite sign but an equal magnitude of 10⁻¹⁰ statcoulomb10⁻¹⁰ statcoulomb corresponds to approximately 0.2083 units of elementary charge. (generally called e.s.u. (electrostatic unit) in older scientific literature), which were separated by 1

ångström The angstromEntry "angstrom" in the Oxford online dictionary. Retrieved on 2019-03-02 from https://en.oxforddictionaries.com/definition/angstrom.Entry "angstrom" in the Merriam-Webster online dictionary. Retrieved on 2019-03-02 from https://www.m ...

.The ångström is within an order of magnitude of the nuclear separation for a typical

covalent bond A covalent bond is a chemical bond that involves the sharing of electrons to form electron pairs between atoms. These electron pairs are known as shared pairs or bonding pairs. The stable balance of attractive and repulsive forces between ato ...

. :1 Å = 100 pm = 10⁻⁸ cm = 10⁻¹⁰ m. This gave a convenient unit for molecular dipole moments. : Typical dipole moments for simple diatomic molecules are in the range of 0 to 11 D. Symmetric homoatomic species, e.g.

chlorine Chlorine is a chemical element with the symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate between them. Chlorine i ...

, Cl₂, have zero dipole moment, and highly ionic molecular species have a very large dipole moment, e.g. gas-phase

potassium bromide Potassium bromide ( K Br) is a salt, widely used as an anticonvulsant and a sedative in the late 19th and early 20th centuries, with over-the-counter use extending to 1975 in the US. Its action is due to the bromide ion ( sodium bromide is equa ...

, KBr, with a dipole moment of 10.41 D.''Physical chemistry'' 2nd Edition (1966) G. M. Barrow. McGraw-Hill. The debye is still used in

atomic physics Atomic physics is the field of physics that studies atoms as an isolated system of electrons and an atomic nucleus. Atomic physics typically refers to the study of atomic structure and the interaction between atoms. It is primarily concerned wit ...

and

chemistry Chemistry is the scientific study of the properties and behavior of matter. It is a natural science that covers the elements that make up matter to the compounds made of atoms, molecules and ions: their composition, structure, proper ...

because SI units have until recently been inconveniently large. The smallest SI unit of electric dipole moment is the quectocoulomb-metre, which corresponds to roughly 0.3 D.With a value of 10⁻³⁰,

quecto- A metric prefix is a unit prefix that precedes a basic unit of measure to indicate a multiple or submultiple of the unit. All metric prefixes used today are decadic. Each prefix has a unique symbol that is prepended to any unit symbol. The pr ...

is the smallest

SI prefix The International System of Units, known by the international abbreviation SI in all languages and sometimes pleonastically as the SI system, is the modern form of the metric system and the world's most widely used system of measurement. ...

, accepted as an SI prefix by the CGPM on 18 November 2022.

Notes

References

{{reflist Non-SI metric units Peter Debye Centimetre–gram–second system of units

See also

Notes

References