Question

The coordination environment of \( \text{Ca}^{2+} \) ion in its complex with \( \text{EDTA}^{4-} \) is:

• A. tetrahedral
• B. octahedral
• C. square planar
• D. trigonal prismatic

Answer 1

The Correct Option is B

To determine the coordination environment of the \( \text{Ca}^{2+} \) ion in its complex with \( \text{EDTA}^{4-} \), we need to understand how \( \text{EDTA}^{4-} \) acts as a ligand and coordinates with metal ions.

Step 1: Understanding EDTA as a ligand.

• \( \text{EDTA}^{4-} \) (ethylenediaminetetraacetate ion) is a hexadentate ligand, meaning it can form six bonds with a metal ion.
• It has four oxygen atoms and two nitrogen atoms that can donate electrons to the metal ion, effectively occupying six coordination sites around the metal ion.

Step 2: Coordination Geometry of \( \text{Ca}^{2+} \) with EDTA.

• The complex formation with \( \text{Ca}^{2+} \) involving \( \text{EDTA}^{4-} \) typically results in an octahedral coordination geometry.
• This is because the six donor atoms of \( \text{EDTA}^{4-} \) create a six-coordinate complex, which is characteristically octahedral in geometry for most transition metal complexes.

Step 3: Conclusion and Verification.

• \(ext{Ca}^{2+} \) ion forms an octahedral complex with \(\text{EDTA}^{4-}\) because this coordination geometry is the most common for metal ions coordinated with six ligand\)
• Ruling out other options:
  • Tetrahedral: Typically occurs with four-coordinate complexes, not six.
  • Square Planar: Also associated with four-coordinate complexes, especially with transition metals like Pd, Pt, etc.
  • Trigonal Prismatic: A rare geometry that is not typical for simple \( \text{EDTA}^{4-} \) complexes with alkaline earth metals like calcium.

Thus, the correct answer is that the coordination environment of \( \text{Ca}^{2+} \) ion in its complex with \( \text{EDTA}^{4-} \) is octahedral.

Answer 2

To determine the coordination environment of the \( \text{Ca}^{2+} \) ion in its complex with \( \text{EDTA}^{4-} \), we need to understand the structure and binding nature of \( \text{EDTA}^{4-} \).

\( \text{EDTA}^{4-} \) (ethylenediaminetetraacetic acid) is a hexadentate ligand, which means it can form six bonds with a metal ion. It does this by using its four carboxylate groups and two amine groups. This ability to form six coordinate bonds with a metal ion typically leads to an octahedral geometry.

Let's evaluate each option:

• Tetrahedral: This geometry usually arises when a metal ion is coordinated by four ligands. Since \( \text{EDTA}^{4-} \) binds through six sites, this geometry is not possible for the \( \text{EDTA}^{4-} \) complex.
• Octahedral: This is the most common geometry for metal ions coordinated by six ligands or binding sites, which matches the hexadentate nature of \( \text{EDTA}^{4-} \). Thus, the coordination environment of \( \text{Ca}^{2+} \) with \( \text{EDTA}^{4-} \) is octahedral.
• Square planar: This geometry typically occurs with complexes involving specific types of ligands and transition metals, particularly those with a d8 electronic configuration. It is not relevant here because the \( \text{Ca}^{2+} \) and \( \text{EDTA}^{4-} \) combination is not known to form square planar complexes.
• Trigonal prismatic: This is a less common coordination geometry and does not match the classical 6-coordinate binding expected with \( \text{EDTA}^{4-} \).

Based on the above analysis, the correct choice is \(octahedral\) because \( \text{EDTA}^{4-} \) provides six coordination sites equating to an octahedral coordination environment.