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

metric Metric or metrical may refer to: Measuring * 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 ...

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 Chemical polarity, polarity. The International System of Units, SI unit for electric ...

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. The dipole itself is a vector whose direction coincides with the position vector of the positive charge with respect to the negative charge: : p = ''q''r. named in honour of the physicist Peter J. W. Debye. It is defined as

statcoulomb The statcoulomb (statC), franklin (Fr), or electrostatic unit of charge (esu) is the unit of measurement for electrical charge used in the centimetre–gram–second electrostatic units variant (CGS-ESU) and Gaussian systems of units. In term ...

centimetre upright=1.35, Different lengths as in respect to the electromagnetic spectrum, measured by the metre and its derived scales. The microwave is in-between 1 meter to 1 millimeter. A centimetre (International spelling) or centimeter (American ...

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 angstrom (; ) is a unit of length equal to m; that is, one ten- billionth of a metre, a hundred-millionth of a centimetre, 0.1 nanometre, or 100 picometres. The unit is named after the Swedish physicist Anders Jonas Ångström (1814� ...

.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 atom ...

. : 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. Molecules with symmetry point groups or containing inversion symmetry do not have a permanent dipole moment, while 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 ed. (1966). G. M. Barrow. McGraw-Hill. A proton and an electron 1 Å apart have a dipole moment of 4.8 D. 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 physical science within the natural sciences that studies the chemical elements that make up matter and chemical compound, compounds made of atoms, molecules a ...

because SI units have until recently been inconveniently large. The smallest SI unit of electric dipole moment is the quectocoulomb-metre,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 pre ...

is the smallest

SI prefix The International System of Units, internationally known by the abbreviation SI (from French ), is the modern form of the metric system and the world's most widely used system of measurement. It is the only system of measurement with official st ...

, accepted as an SI prefix by the CGPM on 18 November 2022. which corresponds closely to 0.3 D.

Notes

References

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

See also

Notes

References