Question

Drawing Conclusions An element that disproportionates must have at least how many different oxidation states? Explain your reasoning.

Short answer

Three oxidation states.

Step-by-step solution

- Understanding Disproportionation

Disproportionation is a type of redox reaction in which a single substance is simultaneously oxidized and reduced, forming two different products.

- Identifying Oxidation States

For disproportionation to occur, the element involved must be able to exhibit at least two different oxidation states in the products, apart from its original state.

- Minimum Number of Oxidation States

Since an element must change its oxidation state to at least two different values from its initial state during disproportionation, it must have at least three different possible oxidation states.

Key concepts

Oxidation States

Oxidation states are used to keep track of how many electrons an atom gains, loses, or shares during a chemical reaction.
They are essential for understanding redox reactions, including disproportionation.

An oxidation state is essentially a number assigned to an element in a compound. This number can be positive, negative, or zero.
For example, in water (H₂O), hydrogen has an oxidation state of +1 and oxygen has an oxidation state of -2.

To determine the oxidation state:

• Use the periodic table as a guide; elements from Group 1 have an oxidation state of +1, while Group 2 elements have a +2 state.
• Follow the general rules: atoms in their elemental form have an oxidation state of 0, and for a molecule like O₂ or N₂, each atom has an oxidation state of 0.
• In compounds, sum up the oxidation states of all atoms to match the overall charge of the molecule or ion.

Redox Reactions

Redox reactions are chemical reactions where the oxidation states of atoms change. These reactions involve two key processes: oxidation and reduction.

Oxidation refers to the loss of electrons and an increase in oxidation state.
On the other hand, reduction involves the gain of electrons and a decrease in oxidation state.

• In a redox reaction, one species will lose electrons (oxidized) and another species will gain those electrons (reduced).
• For instance, in the reaction between hydrogen and oxygen to form water, hydrogen is oxidized (losing electrons) and oxygen is reduced (gaining electrons).
• The substance that donates electrons acts as the reducing agent, and the substance that accepts electrons is the oxidizing agent.

Chemical Reactions

Chemical reactions involve the breaking and forming of bonds between atoms, leading to the transformation of substances.
These reactions can be classified into several types, such as combination, decomposition, single-replacement, and double-replacement reactions.
An important subset of reactions is redox reactions, which includes disproportionation reactions.

• In a combination reaction, two or more substances combine to form a single product.
• Decomposition reactions involve a single compound breaking down into two or more products.
• Single-replacement reactions occur when one element replaces another element in a compound.
• Double-replacement reactions involve the exchange of ions between two compounds to form new compounds.

Disproportionation reactions are unique because a single substance undergoes both oxidation and reduction.
The key to understanding these reactions is recognizing that the element must exhibit at least three different oxidation states: the initial state and two different final states.