The oxidation state and valency of Al in [AlCl(H₂O)₅]²⁺ :

• A. +6 and +3
• B. +3 and +6
• C. +6, +6
• D. +3 and +3

To determine the oxidation state and valency of aluminum (Al) in the complex ion [AlCl(H₂O)₅]²⁺, we need to analyze the components of the complex and how they interact with each other. Let's break it down step by step.

Understanding the Components

The complex ion consists of aluminum, a chloride ion (Cl⁻), and five water molecules (H₂O). In coordination compounds, the central metal ion (in this case, Al) can have different oxidation states depending on its bonding with ligands and counterions.

Oxidation State of Aluminum

First, let's assign oxidation states to the components:

• The chloride ion (Cl⁻) has an oxidation state of -1.
• Each water molecule (H₂O) is a neutral ligand, contributing an oxidation state of 0.

Now, we can set up an equation based on the overall charge of the complex ion. The complex [AlCl(H₂O)₅]²⁺ has a total charge of +2. If we let the oxidation state of aluminum be x, we can write the equation:

x (oxidation state of Al) + (-1) (from Cl) + 0 (from 5 H₂O) = +2

This simplifies to:

x - 1 = +2

x = +3

Valency of Aluminum

Valency refers to the ability of an atom to bond with other atoms, which is often related to the number of electrons it can lose, gain, or share. In this case, aluminum has an oxidation state of +3, meaning it can lose three electrons to form bonds. Therefore, the valency of aluminum in this complex is also +3.

Final Analysis

In summary, the oxidation state of aluminum in [AlCl(H₂O)₅]²⁺ is +3, and its valency is also +3. Therefore, the correct answer to your question is:

D. +3 and +3

Why This Matters

Understanding oxidation states and valency is crucial in coordination chemistry, as it helps predict the behavior of metal complexes in various chemical reactions. This knowledge is foundational for fields such as biochemistry, materials science, and environmental chemistry, where metal ions play significant roles.