"Basic oxides" is a compounds word of "Basic" and "oxides". The word oxides referred to the chemical compounds that one or more oxygen atoms combined with another element such as H2O or CO2. Based on their acid-base characteristics oxides can be classified into four categories: acidic oxides, basic oxides, and amphoteric oxides and neutral oxides. Basic oxides, can also called base anhydrides which means "a base without water", are usually formed by reacting of oxygen with metals, especially alkali and alkaline earth metals. Both of them are ionicoxide and can dissolve in water to form basic solutions of the metal hydroxide, whereas non-metals usually form acidic oxides. Basic oxide Li2O becomes base LiOH and BaO becomes Ba2 after react with water. In general, basicity of their oxides increases when the elements located downward at the left side of a periodic table, as the element become more metallic. Alkali Metals Alkaline Earth Metals Examples include:
Sodium oxide, which reacts with water to produce sodium hydroxide
Potassium reacts with oxygen to form superoxide. KO2
K + O2 → KO2
Properties
The molecules that contain the group of H-O-X can behave normally as acids but when the hydroxide ion is produced they can behave as bases. The O-X bond will remain intact and become polar and the weak O-H bond will tend to break, releasing a proton when the H-O-X grouping is dissolved in water. The O-X bond will become ionic and breakdown in polar water if X has very low electronegativity. For example, when NaOH and KOH which are ionic substances dissolve in water they will produce basic solutions of the metal cation and hydroxide ion. These principles can explain the base behavior when they are dissolved in water by recognizing that the oxide ion has a high affinity for protons. Most basic oxides are ionic in nature base on the difference of electronegativity of oxygen and metals. Dissolving basic oxide in water can increase pH of water because basic oxides release hydroxide ions to the water.
Examples
All oxides in Group 1 & 2 elements are basic, they react with water to form a base:
* Lithium oxide reacts with water to produce Lithium hydroxide: Li2O + H2O → 2 Li+ + 2 OH−
* Sodium oxide reacts with water to produce Sodium hydroxide: Na2O + H2O → 2 NaOH
* Potassium oxide reacts with water to produce Potassium hydroxide: K2O + H2O → 2 KOH
* Rubidium oxide reacts with water to produce Rubidium hydroxide: Rb2O + H2O → 2 RbOH
* Caesium oxide reacts with water to produce Caesium hydroxide: Cs2O + H2O → 2 CsOH
* Magnesium oxide reacts with water to produce Magnesium hydroxide: MgO + H2O → Mg2
* Calcium oxide reacts with water to produce Calcium hydroxide: CaO + H2O → Ca2
* Strontium oxide reacts with water to produce Strontium hydroxide: SrO + H2O → Sr2
* Barium oxide reacts with water to produce Barium hydroxide: BaO + H2O → Ba2
Some oxide in Group 13 element is basic, it reacts with water to form a base:
* Thallium oxide reacts with water to produce Thallium hydroxide: Tl2O + H2O → 2 TlOH
Some oxide in Group 15 element is basic, it reacts with water to form a base:
* Bismuth Oxide reacts with water to produce Bismuth hydroxide: Bi2O3 + 3H2O → 2 Bi3
In neutralization reactions, basic oxides reacts with an acid to form salt and water:
