What is the Difference Between Coordination Number and Oxidation Number

In chemistry, understanding the properties and behavior of elements and compounds is essential for unraveling the intricacies of chemical reactions and structures. Coordination number and oxidation number are fundamental concepts that offer unique insights into the arrangement and behavior of atoms within compounds. While both concepts are vital for understanding chemical properties, they represent different aspects of chemical behavior.

What is the difference between coordination number and oxidation number? Coordination number is the number of ligands surrounding a central metal ion in a complex whereas oxidation number is the measure of the electron transfer between atoms in a compound, indicating the apparent charge of an atom within the compound.

Key Areas Covered

1. What is Coordination Number  
      – Definition, Features, Role
2. What is Oxidation Number
      – Definition, Features, Role
3. Similarities Between Coordination Number and Oxidation Number
      – Outline of Common Features
4. Difference Between Coordination Number and Oxidation Number
      – Comparison of Key Differences
5. FAQ: Coordination Number and Oxidation Number
      – Frequently Asked Questions

Key Terms

Coordination Number, Oxidation Number

What is Coordination Number

Coordination number is a fundamental concept in chemistry that describes the number of ligands or atoms directly attached to a central metal ion in a complex. This parameter plays a crucial role in determining the geometry and stability of coordination compounds, which are essential in various chemical and biological processes.

In coordination compounds, the central metal ion acts as a Lewis acid, capable of accepting electron pairs from surrounding ligands. The coordination number is indicative of the metal ion’s ability to form bonds and influences the overall structure of the complex. Common coordination numbers include 2, 4, 6, and 8, although others are possible depending on the metal and ligands involved.

Figure 1: Zirconium Borohydride, which features 12-Coordinate Metal Centre

A coordination number of 2 often results in linear geometries, while a coordination number of 4 commonly leads to tetrahedral or square planar structures. A coordination number of 6 frequently results in octahedral geometries, and 8 may lead to square antiprismatic or dodecahedral arrangements. These geometries are governed by the need for metal-ligand interactions to achieve maximum stability.

The coordination number is a key factor in the thermodynamic and kinetic aspects of complex formation. It influences the overall stability of a complex and its reactivity in various chemical reactions. Moreover, the coordination number is essential in predicting the magnetic properties of coordination compounds, as different geometries lead to distinct electronic configurations.

What is Oxidation Number

Oxidation number, also known as oxidation state, is a concept in chemistry that helps determine the electron distribution within a compound or molecule. It reflects the apparent charge of an atom when it forms a chemical bond, indicating the degree of electron loss or gain.

Atoms exhibit oxidation numbers based on their electronegativity and tendency to gain or lose electrons. Elements in their elemental state typically have an oxidation number of zero. In compounds, oxidation numbers can be positive, negative, or zero, representing the electron transfer during chemical reactions.

The rules for assigning oxidation numbers involve considering the electronegativity of elements and their common oxidation states. For example, alkali metals generally have an oxidation number of +1, alkaline earth metals +2, and oxygen -2.

Oxidation numbers are crucial for balancing redox reactions, where electrons are transferred between species. The increase or decrease in oxidation numbers reveals the flow of electrons, helping chemists understand the underlying chemical transformations.

Similarities Between Coordination Number and Oxidation Number

1. Both coordination number and oxidation number are concepts used in chemistry to describe the properties and behavior of compounds.
2. They provide important information about the structure and arrangement of atoms within molecules or ions.
3. Both coordination number and oxidation number are used to predict how compounds will react with each other and with other substances.

Difference Between Coordination Number and Oxidation Number

Definition

The coordination number refers to the number of ligands surrounding a central metal ion in a complex, while the oxidation number represents the apparent charge of an atom within a molecule or ion, indicating the electron distribution.

Nature

Coordination number is a geometric property related to the spatial arrangement in coordination compounds, while oxidation number is a chemical property associated with the electron transfer in a chemical species.

Expressed as

While coordination number is a dimensionless quantity, simply indicating the count of surrounding ligands, oxidation number is expressed in terms of electric charge (e.g., +2, -3), representing the electron gain or loss.

Conclusion

In conclusion, coordination number and oxidation number are distinct concepts that help us understand chemical structures and reactions. Coordination number determines how ligands are arranged around a central metal ion in coordination compounds, affecting their stability and reactivity. Oxidation number shows us how electrons are distributed within a molecule or ion, which helps balance redox reactions. Understanding the similarities and differences between coordination number and oxidation number helps chemists better grasp molecular arrangements and electron transfers, providing valuable tools for their work.

FAQ: Coordination Number and Oxidation Number

1. Is coordination number and the oxidation number the same?

No, coordination number and oxidation number are not the same. They represent two different concepts in chemistry. They are involved in the arrangement of atoms in the compound.

2. How do you limit oxidation?

Oxidation can be reduced by lowering exposure to environmental pollutants with oxidizing properties. Moreover, oxidizing agents oxidizes the compounds by undergoing reduction themselves.

3. How is oxidation number calculated in an ion in uniatomic state?

In a uniatomic ion, the oxidation state or number is equal to the charge of the ion. For example, Fe3+ has an oxidation number of +3.

4. Can the oxidation number be zero?

The oxidation number of an atom is zero in a neutral substance that contains atoms of only one element. For example, oxidation number of Fe, S, O in its neutral atomic state is zero. Another example is O2, where the oxidation number is zero in O.

5. What increases oxidation?

Oxidation is increased by the loss of negatively charged electrons. When electrons are lost from a compound, it is said to be oxidized.

Reference:

1. “Oxidation Number.” Encyclopedia Britannica.
2. “Coordination Number.” Encyclopedia Britannica.

Image Courtesy:

1. “Zirconium-borohydride-3D-balls-A” By Ben Mills – Own work (Public Domain) via Commons Wikimedia
2. “Period 2 oxidation numbers” By Albris – Own work (CC BY-SA 4.0) via Commons Wikimedia