Question

Write equations for the stepwise formation of each of the following complex ions. a. \(\mathrm{Ni}(\mathrm{CN})_{4}^{2-}\) $$ \text { b. } \mathrm{V}\left(\mathrm{C}_{2} \mathrm{O}_{4}\right)_{3}{ }^{3-} $$

Short answer

Short Answer: The stepwise formation equations for the complex ions are as follows: a. Ni(CN)₄²⁻ : 1. Ni²⁺ + CN⁻ → NiCN²⁻ 2. NiCN²⁻ + CN⁻ → Ni(CN)₂³⁻ 3. Ni(CN)₂³⁻ + CN⁻ → Ni(CN)₃⁴⁻ 4. Ni(CN)₃⁴⁻ + CN⁻ → Ni(CN)₄²⁻ b. V(C₂O₄)₃³⁻ : 1. V³⁺ + C₂O₄²⁻ → VC₂O₄⁺ 2. VC₂O₄⁺ + C₂O₄²⁻ → V(C₂O₄)₂⁻ 3. V(C₂O₄)₂⁻ + C₂O₄²⁻ → V(C₂O₄)₃³⁻

Step-by-step solution

Identify the central metal ion and ligands

In this complex ion, the central metal ion is Ni²⁺ (nickel ion) and the ligand is the CN⁻ ion (cyanide ion). There are 4 CN⁻ ions surrounding the Ni²⁺ ion.

Write the stepwise formation equations for the complex ion

Now we will write the equations for the formation of the Ni(CN)₄²⁻ complex ion as the CN⁻ ions progressively bind to the Ni²⁺ ion. 1. Ni²⁺ + CN⁻ → NiCN²⁻ 2. NiCN²⁻ + CN⁻ → Ni(CN)₂³⁻ 3. Ni(CN)₂³⁻ + CN⁻ → Ni(CN)₃⁴⁻ 4. Ni(CN)₃⁴⁻ + CN⁻ → Ni(CN)₄²⁻ b. V(C₂O₄)₃³⁻

Identify the central metal ion and ligands

In this complex ion, the central metal ion is V³⁺ (vanadium ion) and the ligand is the C₂O₄²⁻ ion (oxalate ion). There are 3 C₂O₄²⁻ ions surrounding the V³⁺ ion.

Write the stepwise formation equations for the complex ion

Now we will write the equations for the formation of the V(C₂O₄)₃³⁻ complex ion as the C₂O₄²⁻ ions progressively bind to the V³⁺ ion. 1. V³⁺ + C₂O₄²⁻ → VC₂O₄⁺ 2. VC₂O₄⁺ + C₂O₄²⁻ → V(C₂O₄)₂⁻ 3. V(C₂O₄)₂⁻ + C₂O₄²⁻ → V(C₂O₄)₃³⁻ These are the stepwise formation equations for the given complex ions.

Key concepts

Stepwise Formation

Stepwise formation is an important concept in chemistry, particularly when studying the creation of complex ions. To understand it, let's imagine we are assembling a complex ion piece by piece. Each piece represents a ligand attaching to a central metal ion. With stepwise formation, each ligand joins in a separate and distinct step.
This process is simple when broken down:

• The first step involves the combination of a central metal ion with one ligand.
• In subsequent steps, additional ligands attach to this initial metal-ligand assembly.

Think of it as attaching more pieces to a central core until the complete ion is formed. This methodical process allows chemists to understand how complex ions are built and how each part contributes to the ion's overall stability and characteristics.

Ligands

Ligands are fundamental in the formation of complex ions, serving as the attachments or 'arms' that bind to central metal ions. They are atoms or molecules that donate electrons to form a coordinate bond with the metal ion.
Ligands can vary greatly:

• They range from simple ions like CN⁻ (cyanide) to larger molecules like C₂O₄²⁻ (oxalate).
• Each ligand has a specific number of sites to attach or bind, determining its classification as unidentate (bonding at one site), bidentate (two sites), or polydentate (multiple sites).

This ability to bind gives ligands their role in stabilizing metal ions and affecting properties like color and reactivity of the complexes they form. In complex ion formation, selecting the right ligand is crucial for determining the characteristics of the final compound.

Coordination Chemistry

Coordination chemistry studies compounds made from a central metal atom or ion surrounded by molecules or ions called ligands. The field examines how these bonds form and the properties that result.
Key concepts include:

• Coordinate bonds, also known as dative covalent bonds, are formed when a ligand donates a pair of electrons to the metal ion.
• The coordination number is the number of ligand donor atoms attached to the central metal ion, influencing the structure and shape of the complex.

This branch of chemistry plays a crucial role in understanding biochemical processes and industrial applications, providing insights into the behavior and stability of various metal complexes.

Metal Ions

Metal ions are at the heart of complex ion formation, serving as the central entity to which ligands attach. These ions usually come from transition metals, known for their ability to form stable complexes.
Metal ions possess distinct properties:

• These properties include variable oxidation states and the ability to form colored compounds.
• They can accept electrons from ligands to establish bonds, making them versatile in forming diverse structures.

Understanding metal ions' behavior is vital for predicting how they will interact with ligands, influencing the resulting compound's stability and functionality.