Charge number (''z'') refers to a quantized value of electric charge, with the

quantum In physics, a quantum (plural quanta) is the minimum amount of any physical entity (physical property) involved in an interaction. The fundamental notion that a physical property can be "quantized" is referred to as "the hypothesis of quantizati ...

of electric charge being the

elementary charge The elementary charge, usually denoted by is the electric charge carried by a single proton or, equivalently, the magnitude of the negative electric charge carried by a single electron, which has charge −1 . This elementary charge is a fundame ...

, so that the charge number equals the electric charge (''q'') in coulombs divided by the elementary-charge constant (''e''), or ''z'' = ''q''/''e''. The charge numbers for

ion An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by conv ...

s (and also

subatomic particle In physical sciences, a subatomic particle is a particle that composes an atom. According to the Standard Model of particle physics, a subatomic particle can be either a composite particle, which is composed of other particles (for example, a prot ...

s) are written in superscript, e.g. Na⁺ is a sodium ion with charge number positive one (an electric charge of one elementary charge).

Atomic numbers The atomic number or nuclear charge number (symbol ''Z'') of a chemical element is the charge number of an atomic nucleus. For ordinary nuclei, this is equal to the proton number (''n''p) or the number of protons found in the nucleus of ever ...

(''Z'') are a special case of charge numbers, referring to the charge number of an atomic nucleus, as opposed to the net charge of an atom or ion. All particles of

ordinary matter In classical physics and general chemistry, matter is any substance that has mass and takes up space by having volume. All everyday objects that can be touched are ultimately composed of atoms, which are made up of interacting subatomic part ...

have integer-value charge numbers, with the exception of

quark A quark () is a type of elementary particle and a fundamental constituent of matter. Quarks combine to form composite particles called hadrons, the most stable of which are protons and neutrons, the components of atomic nuclei. All commonly o ...

s, which cannot exist in isolation under ordinary circumstances (the

strong force The strong interaction or strong force is a fundamental interaction that confines quarks into proton, neutron, and other hadron particles. The strong interaction also binds neutrons and protons to create atomic nuclei, where it is called the ...

keeps them bound into

hadron In particle physics, a hadron (; grc, ἁδρός, hadrós; "stout, thick") is a composite subatomic particle made of two or more quarks held together by the strong interaction. They are analogous to molecules that are held together by the e ...

s of integer charge numbers).

Charge numbers in chemistry

Charge number or valence of an

is the coefficient that, when multiplied by the

, gives the ion's

charge Charge or charged may refer to: Arts, entertainment, and media Films * ''Charge, Zero Emissions/Maximum Speed'', a 2011 documentary Music * ''Charge'' (David Ford album) * ''Charge'' (Machel Montano album) * '' Charge!!'', an album by The Aqu ...

. For example, the charge on a

chloride The chloride ion is the anion (negatively charged ion) Cl−. It is formed when the element chlorine (a halogen) gains an electron or when a compound such as hydrogen chloride is dissolved in water or other polar solvents. Chloride salts ...

ion,

\mathrm^-

, is

-1 \cdot e

, where e is the elementary charge. This means that the charge number for the ion is

-1

z

is used as the symbol for the charge number. In that case, the charge of an ion could be written as

Q = z e

. The charge number in chemistry normally relates to an electric charge. This is a property of specific subatomic atoms. These elements define the electromagnetic contact between the two elements. A chemical charge can be found by using the periodic table. An element's placement on the

periodic table The periodic table, also known as the periodic table of the (chemical) elements, is a rows and columns arrangement of the chemical elements. It is widely used in chemistry, physics, and other sciences, and is generally seen as an icon of ch ...

indicates whether its chemical charge is negative or positive. Looking at the table, one can see that the positive charges are on the left side of the table and the negative charges are on the right side of the table. Charges that are positive are called cations. Charges that are negative are called anions. Elements in the same group have the same charge. A group in the periodic table is a term used to represent the vertical columns. The

noble gases The noble gases (historically also the inert gases; sometimes referred to as aerogens) make up a class of chemical elements with similar properties; under standard conditions, they are all odorless, colorless, monatomic gases with very low che ...

of the periodic table do not have a charge because they are nonreactive. Noble gases are considered stable since they contain the desired eight electrons. The other atoms or ions have charges because they are very reactive and want to react with another atom or ion to become stable. When elements are bonded, they can either be bonded by ionic bonding or covalent bonding. When elements bond between positive and negative charged atoms, their charges will be switched and carried down on the other element to combine them equally. This is shown below. Using the chart provided, if ammonium with a plus 1 charge is combined with an acetate ion with a negative 1 charge, the charges will be cancelled out, shown in the figure below. :NH4+ + C2H3O2^- -> NC2H7O2 Another example below. :2 NH4+ + CO3^2- -> (NH4)2CO3 both NC2H7O2 and (NH4)2CO3 are

salts In chemistry, a salt is a chemical compound consisting of an ionic assembly of positively charged cations and negatively charged anions, which results in a compound with no net electric charge. A common example is table salt, with positively cha ...

. Charge numbers also help to determine other aspects of chemistry. One example is that someone can use the charge of an ion to find the oxidation number of a monatomic ion. For example, the oxidation number of Li+ is +1. This helps when trying to solve oxidation questions. A charge number also can help when drawing

Lewis dot structures Lewis structures, also known as Lewis dot formulas, Lewis dot structures, electron dot structures, or Lewis electron dot structures (LEDS), are diagrams that show the bonding between atoms of a molecule, as well as the lone pairs of electrons th ...

. For example, if the structure is an ion, the charge will be included outside of the Lewis dot structure. Since there is a negative charge on the outside of the Lewis dot structure, one electron needs to be added to the structure. If the charge was positive, an electron would be lost and taken away.

Charge numbers in nuclear and hadron physics

For an atomic nucleus, which can be regarded as an ion having stripped off all electrons, the charge number is identical with the atomic number ''Z'', which corresponds to the number of

protons A proton is a stable subatomic particle, symbol , H+, or 1H+ with a positive electric charge of +1 ''e'' elementary charge. Its mass is slightly less than that of a neutron and 1,836 times the mass of an electron (the proton–electron m ...

in ordinary atomic nuclei. Unlike in chemistry, subatomic particles with electric charges of two elementary charges (e.g. some delta baryons) are indicated with a superscript "++" or "−−". In chemistry, the same charge numbers are usually indicated as superscript "+2" or "−2".

Charge numbers in elementary-particle physics

In particle physics, the charge number is a (derived) flavor quantum number. For

color-charged Color charge is a property of quarks and gluons that is related to the particles' strong interactions in the theory of quantum chromodynamics (QCD). The "color charge" of quarks and gluons is completely unrelated to the everyday meanings of colo ...

particles like quarks and hypothetical

leptoquarks Leptoquarks (LQs) are hypothetical particles that would interact with quarks and leptons. Leptoquarks are color-triplet bosons that carry both lepton and baryon numbers. Their other quantum numbers, like spin, (fractional) electric charge and weak ...

, the charge number is a multiple of 1/3.

References

{{Reflist Units of electrical charge

Charge numbers in chemistry

Charge numbers in nuclear and hadron physics

Charge numbers in elementary-particle physics

See also

References