The metal oxides (also known as basic oxides) are compounds that originate from the combination of a metal and oxygen, with the particularity of being fundamentally linked by a so-called ionic bond. For example: cuprous oxide, cupric oxide, zinc oxide.
They generally have the characteristic to be solid and have a relatively high melting point (precisely this is what is typical for them and what differentiates them from non-metallic oxides, which have a much lower one).
Metal oxides are usually crystalline and at least moderately soluble in water. Metal oxides are good conductors of heat and electricity, which is why they are commonly used for these purposes.
In its composition, metal oxides are binary combinations of a metal with oxygen, with the latter acting with an oxidation number -2. Therefore, it is necessary to take into account the valences of the metal that takes part in the reaction together with the oxygen to have a notion of how many atoms of the element it will be necessary to exchange for each atom of oxygen.
Nomenclature of metal oxides
Oxides of this type have a particularity regarding their traditional nomenclature since it is not easy to put a name to each one because each metallic element sometimes has different oxidation numbers.
- In the event that the metallic element bonded to oxygen has a single oxidation number, the traditional way of naming it will be: oxide + name of the metallic element.
- If you have two oxidation numbers It will be named: oxide + name of the metallic element with the ending “bear” for the one with the lowest oxidation number, and with the ending “ico” for the one with the highest oxidation number.
- If you have three oxidation numbers it will be named: oxide + name of the metallic element with the prefix “hypo” and with the ending “bear” for the one with the lowest oxidation number, with the ending “bear” for the one with the intermediate oxidation number and with the termination “ico” for the one with the highest oxidation number.
- If you have four oxidation numbers it will be named: oxide + name of the metallic element with the prefix “hypo” and with the ending “bear” for the one with the lowest oxidation number, with the ending “bear” for the one with the intermediate oxidation number, with the ending “ico” for the one with the intermediate oxidation number that follows and with the prefix “per” and with the ending “ico” for the one with the highest oxidation number.
On the other hand, metal oxides can also be named using the Stock nomenclature, which consists of naming them by putting: oxide of + metallic element followed by a Roman number in parentheses that corresponds to the oxidation state of the metal.
In addition, there is the systematic nomenclature, which consists of using prefixes and suffixes that indicate the amount of each atom in the compound.
For example, uranium has four oxidation states (3+, 4+, 5+, 6+), so its oxides according to each type of nomenclature can be named:
3+ oxidation state: (UtwoOR3)
- Traditional: hypouranous oxide
- Stock: uranium (III) oxide
- Systematics: diuranium trioxide
Oxidation state 4+: (UOtwo)
- Traditional: uranium oxide
- Stock: uranium (IV) oxide
- Systematics: uranium dioxide
5+ oxidation state: (UtwoOR5)
- Traditional: uranic oxide
- Stock: uranium (V) oxide
- Systematics: uranium pentaoxide
6+ oxidation state: (UO3)
- Traditional: peruranic oxide
- Stock: uranium (VI) oxide
- Systematics: uranium trioxide
Examples of basic or metallic oxides
- Cuprous oxide (CutwoOR). This copper oxide is insoluble in water and organic solvents.
- Cupric oxide (CuO). It is the copper oxide with the highest oxidation number. As a mineral it is known as tenorite.
- Cobaltous oxide (CoO). It is an inorganic monoxide with an olive green or reddish appearance in its crystalline form.
- Auric oxide (AutwoOR3). It is the most stable oxide of gold. It has a reddish-brown color and is insoluble in water.
- Titanium (IV) oxide (TiOtwo). It is naturally found in some minerals, in a spherical shape. It is inexpensive, safe, and abundant.
- Zinc oxide (ZnO). It is a white compound, also known as the white zinc compound. It is slightly soluble in water but very soluble in acids.
- Nickel oxide (NitwoOR3). It is a compound of nickel (it has 77% nickel in its composition). It is also known as black nickel oxide.
- Silver (I) oxide (AgtwoOR). This compound is a fine black or brown powder that is used to prepare other silver compounds.
- Mercuric oxide (HgO). Mercury (II) oxide is also a compound that has an orange or red color, it occurs in a solid state at room temperature.
- Chromic oxide (CrO). It is an inorganic chromium and oxygen compound.
- Barium oxide (BaO). It is a hygroscopic oxide (which absorbs moisture from the environment that surrounds it).
- Chromic oxide (CrtwoOR3). It is an inorganic compound that is used as a pigment, chrome green.
- Plumbous oxide (PbO). With an orange color, it is frequently used in ceramics and in the chemical industry.
- Permanganic oxide (MntwoOR7). It is a very strong oxidant. It has a dark red, or sometimes green, oily appearance.
- Ferrous oxide (FeO). It is a black powder widely used as a pigment.
- Ferric oxide (FetwoOR3). It is the rust that appears when this metal is exposed to air and humidity.
- Calcium oxide (CaO). It is the so-called lime, widely used in construction.
- Lithium oxide (LitwoOR). It is widely used in the manufacture of ceramics.
- Stannous oxide (SnO). It is a bluish-black oxide that is used in the manufacture of glass.
- Stannic oxide (SnOtwo). It is the main mineral of tin, called cassiterite.