Determine the geometry for the following complex ion: [Ni(OH)₄]^2–.

• A. Tetrahedral
• B. Square planar
• C. Octahedral
• D. Linear

Answer: (B)

Verified step by step guidance

1. Identify the central metal ion in the complex. In this case, it is Nickel (Ni).
2. Determine the oxidation state of the central metal ion. Nickel typically has oxidation states of +2 or +3. Here, it is likely +2 due to the overall charge of the complex ion being 2–.
3. Count the number of ligands attached to the central metal ion. In [Ni(OH)4]2–, there are four hydroxide (OH) ligands.
4. Consider the coordination number, which is the number of ligand atoms directly bonded to the central metal ion. Here, the coordination number is 4.
5. Use the coordination number to predict the geometry. A coordination number of 4 can lead to either tetrahedral or square planar geometry. Nickel(II) complexes often exhibit square planar geometry due to the electronic configuration and ligand field stabilization.