Difference Between Monoxide and Dioxide

Key Difference – Monoxide vs Dioxide
 

The terms monoxide and dioxide are used in the nomenclature of oxide  compounds. An oxide is any chemical compound containing at least one oxygen atom bonded to another element. Sometimes the term oxide is used to name the oxide anion (O^2-). Most of the elements can be found naturally in their oxide compound form. Some elements form different oxide compounds based on their oxidation states. The term monoxide is used to name a compound having one oxygen atom bonded to another element. Hence, the term dioxide expresses the presence of two oxygen atoms. Some elements form oxides with more than two oxygen atoms. The key difference between monoxide and dioxide is that monoxide compounds contain one oxygen atom bonded to another element whereas dioxide compounds contain two oxygen atoms bonded to the same atom of a different element.

CONTENTS

1. Overview and Key Difference
2. What is Monoxide
3. What is Dioxide
4. Side by Side Comparison – Monoxide vs Dioxide in Tabular Form
5. Summary

What is Monoxide?

The term monoxide is used to name compounds containing one oxygen atom bonded to another element. when considering the anion, the term monoxide refers to the oxide anion (O^2-). However, in monoxide compounds, the only oxygen atom can be bonded to one atom of the other element or two atoms of it, but not more than two. That is because oxygen atom can form only two covalent bonds in its stable condition.

Group 1 elements of the periodic table can have only the +1 oxidation state. But the oxide anion have -2 oxidation state. Then, the monoxide of group 1 elements have two atoms bonded to the same oxygen atom. but in the case of group 2 elements, their stable oxidation state is +2. Then, one oxygen atom binds to one atom (of group 2 element) to form the monoxide.

Figure 01: A monoxide has one oxygen atom (in red) bonded to another element.

There is a wide variety of monoxide compounds. Some examples are given below.

What is Dioxide?

The term dioxide is used to name compounds containing two oxygen atoms bonded to a different element. These compounds are essentially composed of two oxygen atoms. Most of the times these two oxygen atoms are bonded to the same atom (of the different chemical element).

Figure 02: A dioxide has two oxygen atom (in red).

There are various dioxide compounds. Some examples are given below.

• Carbon dioxide (CO₂)
• Nitrogen dioxide (NO₂)
• Sulfur dioxide (SO₂)
• Barium dioxide (BaO₂)
• Silicon dioxide (SiO₂)

Although H₂O₂ is also composed of two oxygen atoms, it is not considered as a dioxide. It is known as hydrogen peroxide. The reason is, to call an oxide containing two oxygen atoms, a dioxide, the oxidation state of the oxygen atom in that compound should be in its stable state (-2 oxidation state). In H₂O₂, oxygen is in -1 oxidation state, thus, it is known as a peroxide.

What is the Difference Between Monoxide and Dioxide?

Summary – Monoxide vs Dioxide

Monoxide and dioxide are terms used to name different oxides based on the oxygen atoms present in their chemical structure. The difference between monoxide and dioxide is that monoxide compounds contain one oxygen atom bonded to another element whereas dioxide compounds contain two oxygen atoms bonded to the same atom of a different element.

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Reference:

1.“Monoxide.” Wikipedia, Wikimedia Foundation, 31 Dec. 2017. Available here  
2.“GCSE Chemistry – Oxygen and oxides – Revision 5.” BBC Bitesize, BBC. Available here  

Image Courtesy:

1.’Carbon-monoxide-3D-balls’By Benjah-bmm27 – Own work, (Public Domain) via Commons Wikimedia  
2.’Carbon dioxide 3D ball’By Jynto – Own work (Public Domain) via Commons Wikimedia

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