What is the Difference Between Formal Charge and Oxidation State?

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Formal charge and oxidation state are both ways of assigning electrons to atoms in molecules, but they differ in how they take into account electronegativity. Here are the key differences between the two concepts:

  • Formal Charge: This is the charge an atom would have if all bonding electrons were divided equally between the atoms in a molecule or polyatomic ion. It does not take into account electronegativity, and the charge is determined by the difference between the number of valence electrons in an isolated atom and the number of electrons assigned to the atom in the molecule.
  • Oxidation State: This is a more refined method of assigning electrons, taking into account the electronegativity of the atoms in a molecule or polyatomic ion. The oxidation state is obtained by arbitrarily assigning the electrons of each covalent bond to the more electronegative atom. If two like atoms are joined, each atom is assigned half the bonding electrons.

In summary, the main difference between formal charge and oxidation state is that formal charge does not consider electronegativity, while oxidation state does. Both methods are used to simplify electron-counting in chemical calculations, but oxidation state provides a more accurate representation of the electronic distribution in molecules or ions.

Comparative Table: Formal Charge vs Oxidation State

Formal charge and oxidation state are two different concepts used to describe the distribution of electrons in molecules. Here is a table summarizing the differences between them:

Feature Formal Charge Oxidation State
Definition The hypothetical charge that an atom would have if all bonding electrons were shared equally between atoms in a molecule. A measure of the actual electron density around an atom in a molecule, taking into account the electronegativity of the atoms involved.
Assumption Assumes that electrons in all chemical bonds are shared equally between atoms. Does not assume that electrons in all chemical bonds are shared equally between atoms; considers the electronegativity of the atoms involved.
Calculation Calculated by counting the number of valence electrons, bonded electrons, and lone pairs for each atom in a Lewis structure. Calculated by arbitrarily assigning bonding electrons to the more electronegative atom in a covalent bond.
Purpose Helps in predicting the most appropriate Lewis structure for a given molecule. Helps in defining another somewhat artificial device for keeping track of electrons in complicated reactions.

In summary, formal charge is a concept that assumes electrons in chemical bonds are shared equally between atoms, while oxidation state takes into account the electronegativity of the atoms involved and assigns bonding electrons accordingly. Both concepts help in understanding the distribution of electrons in molecules, but they serve different purposes and are calculated differently.