Determine the oxidation number of sulfur in each of the following substances: (b) sulfurous acid, H2SO3

Key Concepts

Oxidation Number

The oxidation number, or oxidation state, is a theoretical charge assigned to an atom in a compound based on the assumption that electrons are completely transferred. It helps in understanding the electron distribution in molecules and is crucial for identifying redox reactions. Oxidation numbers can be positive, negative, or zero, depending on the atom's electron gain or loss.

Rules for Assigning Oxidation Numbers

There are specific rules for assigning oxidation numbers, such as the oxidation number of an element in its standard state is zero, and the sum of oxidation numbers in a neutral compound must equal zero. For hydrogen, the oxidation number is typically +1, while for oxygen, it is usually -2. These rules guide the determination of oxidation states in complex molecules.

Structure of Sulfurous Acid (H2SO3)

Sulfurous acid (H2SO3) consists of two hydrogen atoms, one sulfur atom, and three oxygen atoms. The sulfur atom is central to the molecule, bonded to one hydroxyl group (–OH) and two oxygen atoms, one of which is double-bonded. Understanding the molecular structure is essential for determining the oxidation state of sulfur, as it influences how electrons are shared or transferred in the compound.