What are hydroxides?


The field of chemistry is quite extensive and in it we can find a large number of important definitions. Perhaps the basis of this science are chemical compounds , substances that are formed by the union of two or more chemical elements . Among these elements we can find hydroxides .

Hydroxides |  What are they, characteristics, classification, how they are formed, uses 

What are hydroxides?

The hydroxides are a type of chemical compound that is formed from the union of an element of type metallic or cationic with an element belonging to the group of hydroxides , or anions .

  • Classification
  • Characteristics of hydroxides
  • Properties
  • How hydroxides are formed
  • Uses and applications
  • Structure
  • Formulation
  • Nomenclature
  • Importance
  • Examples of hydroxides


Hydroxides are classified into three large groups which are:

  • Basics : this type of hydroxide is formed from the reaction that occurs between a metal oxide when it comes into contact with water.
  • Acids : these are formed thanks to the reaction that occurs between an oxide that belongs to a non-metal, in other words an anhydride with water.
  • Amphoteric : this type of hydroxide is responsible for acting as a base against different acids and also act as acids against bases.

Characteristics of hydroxides

Among the most notable characteristics that can be found in hydroxides are the following:

  • Are characterized as inorganic compounds ternary that have in their molecule hydrogen, an oxygen molecule and an element of the metallic type.
  • They can disassociate when dissolved in water.
  • They have a fairly strong basic character because the hydroxyl group has the ability to take up protons .
  • They can turn the color of litmus paper from a shade of red to a blue one.
  • They have the ability to react with acids and thus produce a salt and water.
  • When you do some kind of reaction you can release energy .


Among the physical and chemical properties that hydroxides have, we find the following:

  • When at room temperature and under stable pressure, metal hydroxides are solid and most are white .
  • They have values very high in melting temperature , which mainly are located in Group IA of the periodic table.
  • According to the type of solubility they present in water, hydroxides can be classified as soluble and insoluble .
  • Some of them, when in a liquid or molten state, have the ability to allow the passage of electric current.
  • They have a latent ionic character although it can also be very basic.

How hydroxides are formed

Hydroxides are formed from the combination of a metal oxide and water . For this, it is necessary oxygen , hydrogen and the metal that is part of the compound. In order to achieve the formation of the hydroxide, it is also necessary that a cation and an element of the hydroxide group act, which will act as an anion.

Uses and applications

There are several uses and applications that hydroxides can have, and in fact, many of them are used in activities of daily life . Some are used to highlight pipes, others are also used as digestive and stomach medications , such as magnesium hydroxide.

Some can be used in the construction field in the creation of ceramics. They work very well in the cleaning industry , in textiles and are used in the manufacture of paper and crayons. Some play an important role within the metallurgy industry and in chemical laboratories .


The structure of hydroxides is characterized by being crystalline , very similar to salts or oxides. They can also have a very simple structure and in other cases complex. In hydroxides that have a reduction in their ionic character , a metallic center can be present, which is joined by means of oxygen bridges.


In order to write the molecular formula of a hydroxide, it is important to bear in mind that the hydroxide number must be placed as a subscript and must also coincide with the oxidation number of the metal. To write its formula, you must write the metal and then the functional group OH or hydroxyl group . This hydroxyl group must be subscribed if the valence is greater than the number 1 and must be placed in parentheses. For instance:

PbO2 + H2O → Pb (OH) 4


The nomenclature of hydroxides is performed by first naming the words ” hydroxide of …”. Subsequently, the name of the metal that forms it must be placed and later, the oxidation state number which must be placed in parentheses , and, if this number is greater than one, it must be written in Roman numerals .

You can also use the functional nomenclature to name them and for this a suffix is used in the name of the metal so that in this way it can imply what the oxidation state of the molecule is. When this type of nomenclature is used, the ending ” bear ” will correspond to the state with the least oxidation , or valence is also used , whose ending ” ico ” indicates the highest oxidation .


The hydroxides are very important compounds for human and part of everyday life of virtually all humans because they are ideal for neutralizing the acids which are present in many of the products that are used on day. Many of these compounds are used in the form of drugs and some are even used in clinical laboratories, which gives them even greater relevance.

Examples of hydroxides

Some examples of hydroxides are as follows:

  • Barium hydroxide , Ba (OH) 2
  • Aluminum hydroxide , Al (OH) 3
  • Ferrous hydroxide, Fe (OH) 2
  • Calcium hydroxide, Ca (OH) 2
  • Manganese hydroxide , Mn (OH) 3
  • Magnesium hydroxide, Mg (OH) 2

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