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What are basic oxides?

The basic oxides are inorganic compounds which are formed by bonding between oxygen and metal. They are called basic oxides because they produce alkaline or basic solutions when dissolved in water. Also because they react with acids to form a salt and water through an acid-base neutralization reaction.

Basic oxides are very common. In fact, most metals in nature are found in soils in the form of oxides, which is why they used to be called land in the past.

Basic oxides are of great importance to industry. Many color pigments used in industry are oxides. Other oxides are used as a base for paints, especially titanium, lead and zinc oxides.

Properties of basic oxides

They are binary compounds

These compounds are made up of only two elements: oxygen and a metal. Therefore, they are binary compounds.

Its empirical formula is M 2 O X or MO X / 2

The valence of oxygen in oxides is always -2, so the empirical formulas for oxides are simplified when the valence of the metal is an even number. However, the same does not happen when it is odd.

For example, the empirical formula for sodium oxide is Na 2 O because sodium has valence +1 (odd). In contrast, the empirical formula for calcium oxide is CaO, since calcium has a valence of +2.

They are inorganic compounds, almost always ionic in character

Most basic oxides are crystalline ionic compounds. This includes the oxides of all alkali metals, of all alkaline earths (except beryllium), and of the first series of transition metals.

They have very high melting and boiling points

The ionic bond keeps all the ions that make up the basic oxides tightly bound. This makes them difficult to melt and even more difficult to vaporize. For this reason, they have very high melting and boiling points.

They are solid at room temperature

By the very fact of having high melting points, all basic oxides are solid at room temperature.

They are basic compounds

The reason they are called basic oxides is precisely because of their acid-base properties. Oxides with greater ionic character produce basic solutions when dissolved in water and also react with acids, neutralizing them.

However, it should be noted that not all metal oxides are basic. Some are neutral, some are acidic, and some are amphoteric.

All basic oxides are insoluble in water, with the exception of the alkali metal and barium oxides. However, they are soluble in acid solutions.

How are basic oxides formed?

Basic oxides can form spontaneously when metals are exposed to oxygen in the air. In fact, the corrosion layers that form on the surface of metals consist of different basic oxides.

The metal involved is generally an alkali metal, alkaline earth metal or a transition metal.

Three general reactions can be written for the formation of oxides, depending on whether the valence of the metal is even or odd:

For metals with odd valences:

When the metal has odd valence, the general oxide formation reaction is:

For example, for the formation of sodium oxide, where sodium has valence +1, the reaction is:

Another example is the formation of ferric oxide, in which iron has an oxidation state or valence +3. In this case, the reaction is:

For metals with valence +2:

When the metal has valence +2, the general oxide formation reaction is:

For example, in the case of calcium oxide formation, where calcium has a valence of +2, the reaction is:

For metals with other even valences:

When the metal has even valences other than +2, the general oxide formation reaction is:

An example of this case is the titanium (IV) oxide formation reaction:

Nomenclature of basic oxides

There are three nomenclature systems for basic oxides which are: the traditional nomenclature, the stock and the systematic.

To name an oxide according to the first two nomenclature systems, it is necessary to know the valence of the metal, while for the last one, not.

Traditional nomenclature

As the traditional nomenclature, basic oxides are named beginning with the word or oxide followed by the name of the cation. This last name is constructed by placing the root of the metal name and a system of prefixes and suffixes that indicate the valence of the metal:

Oxide + Prefix-Root-Suffix

The rules for assigning prefixes and suffixes are summarized in the following table:

Number of possible valences

Valencia

Prefix  

Suffix

1 ONLY VALENCIA

Only

___ico

2 VALENCIAS

Higher

— 

___ico

Less 

— 

___bear

3 VALENCIAS

Higher

— 

___ico

Intermediate

___bear

Less 

Hiccup___

___bear

4 VALENCIAS

Higher

Per___

___ico 

Upper intermediate

— 

___ico 

Minor intermediate

— 

___ico 

Less

Hiccup___

___ico 

Example:

The Fe 2 O 3 is iron oxide +3 valence. Iron only has two valences which are +2 and +3, so in this oxide iron has the greater of two valences. For this reason, the suffix ___ico is added to the root of the name of the metal iron which is ferr- .

Therefore, the traditional name of Fe 2 O 3 is:  Ferric Oxide.

Stock nomenclature

In this system, the name is constructed starting with the words oxide , followed by the name of the metal. Finally, its valence in Roman numerals is placed in parentheses:

Oxide + metal name + (valence)

In case the metal only has one valence, this is omitted.

Example:

In Cr 2 O 3 , chromium has a valence of +3, so the Stock name is Chromium (III) oxide.

Systematic nomenclature

This is the only one of the three nomenclatures that does not specify the valence of the metal. Systematic names indicate how many oxygens and metal atoms the compound contains using numerical prefixes.

The name is constructed from the word oxide preceded by the prefix that indicates the number of oxygens , then the article of followed by the name of the respective metal with its prefix .

Prefix-oxide + of + prefix-metal

Some prefixes are:

Number

Prefix

1

Monkey 

2

Gave

3

Tri

4

Tetra

5

Penta …

Example:

In systematic nomenclature, Cr 2 O 3 is called dichrome trioxide, since it has three oxygens and two chromos.

Examples of basic oxides

  • Sodium oxide – Na 2 O
  • Ferric oxide – Fe 2 O 3
  • Iron monoxide – FeO
  • Chromic oxide – Cr 2 O 3
  • Divanadium pentaoxide – V 2 O 5
  • Potassium oxide – K 2 O
  • Barium oxide – BaO

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