Oxidation State Of [Ni(en)3]2+: Explained

by Wholesomestory Johnson 42 views

Hello! I'm here to help you understand the oxidation state of the complex ion [Ni(en)3]2+. I'll provide a clear, detailed, and correct answer. Let's dive in!

Correct Answer

The oxidation state of Nickel (Ni) in the complex ion [Ni(en)3]2+ is +2.

Detailed Explanation

To determine the oxidation state of the central metal atom (Nickel in this case) in a complex ion, we need to consider the charges of the ligands and the overall charge of the complex. Let's break down the process step-by-step.

Key Concepts

  • Oxidation State: The oxidation state (also known as oxidation number) represents the hypothetical charge an atom would have if all bonds to atoms of different elements were completely ionic. It's a way to track the gain or loss of electrons in a chemical species. The oxidation state can be positive, negative, or zero.
  • Complex Ion: A complex ion (also called a coordination complex) is a molecule or ion in which a central metal atom or ion is surrounded by a number of other atoms, ions, or molecules (called ligands). The ligands are attached to the central metal atom by coordinate covalent bonds.
  • Ligands: Ligands are molecules or ions that bind to the central metal atom in a complex ion. They donate a pair of electrons to the metal atom to form a coordinate covalent bond. Ligands can be neutral (e.g., water, ammonia), negatively charged (e.g., chloride, cyanide), or even positively charged.
  • Ethylenediamine (en): Ethylenediamine (en) is a bidentate ligand, meaning it can bind to the central metal atom through two donor atoms. The formula for ethylenediamine is NH2CH2CH2NH2. Importantly, ethylenediamine is a neutral ligand. This means that it does not have a charge associated with it.

Step-by-Step Calculation

  1. Identify the knowns:

    • The overall charge of the complex ion: +2 (given by the 2+ in [Ni(en)3]2+).
    • The charge of the ethylenediamine (en) ligand: 0 (It is a neutral ligand).

  2. Set up the equation: Let 'x' be the oxidation state of Nickel (Ni). The equation is: x + (3 × charge of en) = overall charge of the complex

  3. Plug in the values: x + (3 × 0) = +2

  4. Solve for x: x + 0 = +2 x = +2

So, the oxidation state of Nickel in [Ni(en)3]2+ is +2.

Understanding the Role of Ligands

The ligands in a complex play a crucial role in determining the properties of the complex ion. The type of ligands, their number, and their arrangement around the central metal atom influence the complex's color, reactivity, and stability. In the case of [Ni(en)3]2+, the ethylenediamine ligands provide a specific electronic environment around the nickel ion, which leads to certain chemical behaviors.

Examples to Illustrate Oxidation States

Let's look at some other examples to solidify your understanding:

  • [Cu(H2O)4]2+: Water (H2O) is a neutral ligand (charge = 0). The overall charge of the complex is +2. Therefore, the oxidation state of Copper (Cu) is +2.

    • x + (4 × 0) = +2
    • x = +2

  • [Fe(CN)6]4-: Cyanide (CN-) is a negatively charged ligand (charge = -1). The overall charge of the complex is -4. Therefore, the oxidation state of Iron (Fe) is +2.

    • x + (6 × -1) = -4
    • x - 6 = -4
    • x = +2

  • [Cr(NH3)6]3+: Ammonia (NH3) is a neutral ligand (charge = 0). The overall charge of the complex is +3. Therefore, the oxidation state of Chromium (Cr) is +3.

    • x + (6 × 0) = +3
    • x = +3

  • [PtCl4]2-: Chloride (Cl-) is a negatively charged ligand (charge = -1). The overall charge of the complex is -2. Therefore, the oxidation state of Platinum (Pt) is +2.

    • x + (4 × -1) = -2
    • x - 4 = -2
    • x = +2

These examples demonstrate the importance of understanding ligand charges and applying the correct equation to determine the oxidation state of the central metal atom.

Common Mistakes to Avoid

  • Forgetting the overall charge: Always remember to include the overall charge of the complex ion in your equation. This is crucial for getting the correct answer.
  • Incorrect ligand charges: Make sure you know the charge of each ligand. Refer to a reliable source (like a textbook or a periodic table) if you are unsure. Common neutral ligands include water (H2O), ammonia (NH3), and carbon monoxide (CO).
  • Incorrectly multiplying ligand charges: Remember to multiply the charge of each ligand by the number of ligands present in the complex.
  • Incorrectly solving the equation: Double-check your algebra to ensure you've solved for the oxidation state (x) correctly.

Importance of Oxidation States

Understanding oxidation states is fundamental to understanding chemistry. They help us to:

  • Predict Chemical Behavior: The oxidation state of an element influences its reactivity. For example, a metal in a high oxidation state is often a good oxidizing agent (it readily accepts electrons).
  • Balance Chemical Equations: Oxidation states are essential for balancing redox (reduction-oxidation) reactions. We use them to track the movement of electrons.
  • Name Chemical Compounds: The oxidation state of a metal is often included in the names of its compounds, especially when the metal can have multiple oxidation states (e.g., iron(II) chloride, iron(III) chloride).
  • Understand Coordination Chemistry: Oxidation states are key to understanding the properties of complex ions, as we've seen with [Ni(en)3]2+.

Advanced Considerations

  • Variable Oxidation States: Many transition metals can exhibit multiple oxidation states. For example, iron can exist in the +2 and +3 oxidation states. The specific oxidation state adopted depends on the other elements in the compound and the environmental conditions.
  • Exceptions to the Rules: There are some exceptions to the rules for assigning oxidation states, particularly in complex compounds or when dealing with highly electronegative elements. However, the general principles outlined here are usually sufficient for introductory chemistry.
  • Spectroscopic Techniques: Techniques like X-ray photoelectron spectroscopy (XPS) can be used to experimentally determine the oxidation state of an element in a compound. These techniques provide valuable information about the electronic structure of the compound.

Key Takeaways

  • The oxidation state of Nickel (Ni) in [Ni(en)3]2+ is +2.
  • Ethylenediamine (en) is a neutral ligand (charge = 0).
  • To calculate the oxidation state, use the equation: x + (number of ligands × charge of ligand) = overall charge of the complex.
  • Understanding oxidation states is crucial for understanding chemical reactions, balancing equations, and naming compounds.
  • Always remember to consider the overall charge of the complex ion when calculating the oxidation state.

I hope this explanation has helped you understand the oxidation state of [Ni(en)3]2+! Feel free to ask if you have any further questions. Keep up the great work in your studies!