The chlorite ion, or chlorine dioxide

anion 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 conven ...

, is the halite with the

chemical formula A chemical formula is a way of presenting information about the chemical proportions of atoms that constitute a particular chemical compound or molecule, using chemical element symbols, numbers, and sometimes also other symbols, such as pare ...

of . A chlorite (compound) is a compound that contains this group, with

chlorine Chlorine is a chemical element; it has Symbol (chemistry), 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 ...

in the

oxidation state In chemistry, the oxidation state, or oxidation number, is the hypothetical Electrical charge, charge of an atom if all of its Chemical bond, bonds to other atoms are fully Ionic bond, ionic. It describes the degree of oxidation (loss of electrons ...

of +3. Chlorites are also known as

salt In common usage, salt is a mineral composed primarily of sodium chloride (NaCl). When used in food, especially in granulated form, it is more formally called table salt. In the form of a natural crystalline mineral, salt is also known as r ...

s of chlorous acid.

Compounds

The free acid, chlorous acid HClO₂, is the least stable oxoacid of chlorine and has only been observed as an

aqueous solution An aqueous solution is a solution in which the solvent is water. It is mostly shown in chemical equations by appending (aq) to the relevant chemical formula. For example, a solution of table salt, also known as sodium chloride (NaCl), in water ...

at low concentrations. Since it cannot be concentrated, it is not a commercial product. The

alkali metal The alkali metals consist of the chemical elements lithium (Li), sodium (Na), potassium (K),The symbols Na and K for sodium and potassium are derived from their Latin names, ''natrium'' and ''kalium''; these are still the origins of the names ...

and

alkaline earth metal The alkaline earth metals are six chemical elements in group (periodic table), group 2 of the periodic table. They are beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra).. The elements have very similar p ...

compounds are all colorless or pale yellow, with sodium chlorite (NaClO₂) being the only commercially important chlorite. Heavy metal chlorites (Ag⁺, Hg⁺, Tl⁺, Pb²⁺, and also Cu²⁺ and ) are unstable and decompose explosively with heat or shock. Sodium chlorite is derived indirectly from sodium chlorate, NaClO₃. First, the explosively unstable gas

chlorine dioxide Chlorine dioxide is a chemical compound with the formula ClO2 that exists as yellowish-green gas above 11 °C, a reddish-brown liquid between 11 °C and −59 °C, and as bright orange crystals below −59 °C. It is usually ...

, ClO₂ is produced by reducing sodium chlorate with a suitable reducing agent such as methanol, hydrogen peroxide, hydrochloric acid or sulfur dioxide.

Structure and properties

The chlorite ion adopts a bent molecular geometry, due to the effects of the

lone pair In chemistry, a lone pair refers to a pair of valence electrons that are not shared with another atom in a covalent bondIUPAC ''Gold Book'' definition''lone (electron) pair''/ref> and is sometimes called an unshared pair or non-bonding pair. Lone ...

s on the chlorine atom, with an O–Cl–O bond angle of 111° and Cl–O bond lengths of 156 pm. Chlorite is the strongest oxidiser of the chlorine oxyanions on the basis of standard half cell potentials.

Uses

The most important chlorite is sodium chlorite (NaClO₂), used in the bleaching of textiles, pulp, and paper. However, despite its strongly oxidizing nature, it is often not used directly, being instead used to generate the neutral species

(ClO₂), normally via a reaction with HCl: :5 NaClO₂ + 4 HCl → 5 NaCl + 4 ClO₂ + 2 H₂O

Health risks

In 2009, the California Office of Environmental Health Hazard Assessment, or OEHHA, released a public health goal of maintaining amounts lower than 50 parts per billion for chlorite in drinking water after scientists in the state reported that exposure to higher levels of chlorite affect sperm and thyroid function, cause stomach ulcers, and caused red blood cell damage in laboratory animals. Some studies have indicated that at certain levels chlorite may also be carcinogenic. The federal legal limit in the United States allows chlorite up to levels of 1,000 parts per billion in drinking water, 20 times as much chlorite as California’s public health goal.

Other oxyanions

Several oxyanions of chlorine exist, in which it can assume

s of −1, +1, +3, +5, or +7 within the corresponding anions Cl⁻, ClO⁻, , , or , known commonly and respectively as chloride, hypochlorite, chlorite, chlorate, and perchlorate. These are part of a greater family of other chlorine oxides.

References