Oxide (synonyms: oxide , oxide ) is a binary compound of a chemical element with oxygen in the oxidation state −2, in which oxygen itself is associated only with a less electronegative element. The chemical element oxygen is the second most negative after fluorine in terms of electronegativity ; therefore, almost all compounds of chemical elements with oxygen belong to oxides. Exceptions include, for example, oxygen difluoride OF 2 .
Oxides are a very common type of compounds contained in the earth's crust and in the universe in general. Examples of such compounds are rust , water , sand , carbon dioxide , a number of dyes. Oxides are also a class of minerals , which are compounds of a metal with oxygen (see Oxides ).
Compounds that contain oxygen atoms joined together are called peroxides or peroxides (contain the −O − O− chain), superoxides (contain the O - group
2 ) and ozonides (contain group O -
3 ). Strictly speaking, they do not belong to the category of oxides.
Depending on the chemical properties distinguish:
- Salt-forming oxides :
- basic oxides (for example, sodium oxide Na 2 O, copper (II) oxide CuO): metal oxides, the oxidation state of which is I — II;
- acid oxides (for example, sulfur dioxide (VI) SO 3 , nitric oxide (IV) NO 2 ): metal oxides with oxidation state IV – VII and non-metal oxides;
- amphoteric oxides (for example, zinc oxide ZnO, aluminum oxide Al 2 O 3 ): metal oxides with oxidation state III – IV and exceptions (ZnO, BeO, SnO, PbO);
- Non-salt forming oxides : carbon monoxide (II) CO, nitric oxide (I) N 2 O, nitric oxide (II) NO, silicon oxide (II) SiO.
There are complex oxides that include atoms of two or more elements in the molecule, except oxygen (for example, lithium cobalt oxide (III) Li 2 O · Co 2 O 3 ), and double oxides in which atoms of the same element are included in two or more oxidation states (for example, manganese oxide (II, IV) Mn 5 O 8 ). In many cases, such oxides can be considered as salts of oxygen-containing acids (for example, lithium cobalt (III) oxide can be considered as lithium cobaltite Li 2 Co 2 O 4 , and manganese oxide (II, IV) as manganese orthanganite Mn 3 (MnO 4 ) 2 ).
According to the IUPAC nomenclature , oxides are called the word “oxide”, followed by the name of the chemical element in the genitive case, for example: Na 2 O - sodium oxide , Al 2 O 3 - aluminum oxide . If the element has a variable oxidation state, then the oxidation state indicates its oxidation state in Roman numerals in brackets immediately after the name (without a space ). For example, Cu 2 O is copper (I) oxide, CuO is copper (II) oxide, FeO is iron (II) oxide , Fe 2 O 3 is iron (III) oxide , Cl 2 O 7 is chlorine (VII) oxide .
Other names of oxides are often used according to the number of oxygen atoms: if an oxide contains only one oxygen atom, then it is called monoxide or monoxide , if two - dioxide or dioxide , if three - then trioxide or trioxide , etc. For example: carbon monoxide CO , carbon dioxide CO 2 , sulfur trioxide SO 3 .
The historically formed (trivial) names of oxides are also common, for example, carbon monoxide CO, sulfuric anhydride SO 3 , etc.
At the beginning of the 19th century and earlier refractory oxides practically insoluble in water, chemists called them “earths”.
Oxides with lower oxidation states (suboxides) are sometimes called nitrous oxide and carbon dioxide (for example, carbon monoxide (II) , CO - carbon monoxide; trioxide , C 3 O 2 - carbon dioxide  ; nitric oxide (I) , N 2 O - nitrous oxide; copper oxide (I) , Cu 2 O - copper oxide ).
Oxides with higher oxidation states (for example, iron (III) oxide , Fe 2 O 3 ) are called oxide in accordance with this nomenclature, and double oxides (i.e. with different oxidation states) are called oxide-oxide (Fe 3 O 4 = FeO Fe 2 O 3 - iron oxide-oxide , uranium (VI) -diuran (V) oxide , U 3 O 8 - uranium oxide ).
If any metal gives one basic oxide, then the latter is called oxide, for example, calcium oxide, magnesium oxide, etc .; if there are two, then an oxide with a lower oxygen content is called nitrous oxide, for example iron oxide FeO and oxide Fe 2 O 3 . An oxide with a lower oxygen content than nitrous is called suboxide.- Vukolov S.P. , Mendeleev D.I. Oxides // Encyclopedic Dictionary of Brockhaus and Efron : 86 volumes (82 volumes and 4 additional). - SPb. , 1890-1907.
This nomenclature, however, does not differ in consistency, therefore such names should be considered rather as traditional.
- In the interaction of acid oxide with the basic salt is formed.
- Oxides react with water if a soluble acid or soluble base is formed.
- Basic oxides interact with acids, and acidic with bases.
1. Basic oxide + strong acid → salt + water
2. Strongly basic oxide + water → hydroxide
3. Strongly basic oxide + acid oxide → salt
4. The main oxide + hydrogen → metal + water
Note: metal is less active than aluminum .
1. Acid oxide + water → acid
Some oxides, for example SiO 2 , do not react with water, therefore their acids are obtained indirectly.
2. Acid oxide + basic oxide → salt
3. Acid oxide + base → salt + water
If the acidic oxide is a polybasic acid anhydride , acidic or medium salts may form:
4. Non-volatile oxide + salt1 → salt2 + volatile oxide
5. Acid anhydride 1 + anhydrous oxygen-containing acid 2 → Acid anhydride 2 + anhydrous oxygen-containing acid 1
When interacting with a strong acid or acid oxide, they exhibit the basic properties :
When interacting with a strong base or basic oxide, they exhibit acidic properties :
- (in aqueous solution)
- (during fusion)
- (in aqueous solution)
1. The interaction of simple substances (with the exception of inert gases , gold and platinum ) with oxygen :
When burning in oxygen, alkali metals (except lithium ), as well as strontium and barium , peroxides and superoxide are formed :
2. Firing or burning of binary compounds in oxygen :
3. Thermal decomposition of salts :
4. Thermal decomposition of bases or acids :
5. Oxidation of lower oxides to higher and restoration of higher to lower:
6. The interaction of some metals with water at high temperature:
7. The interaction of salts with acid oxides during the combustion of coke with the release of volatile oxide:
8. The interaction of metals with acids - oxidizing agents :
9. Under the action of water-borne substances on acids and salts :
10. The interaction of salts of weak unstable acids with stronger acids :
- L. B. Dashkevich, V. G. Beilin. Carbon dioxide in organic synthesis / Advances in chemistry. - 1967. - Volume 36. - No. 6. - C. 947–964.