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.
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Approach Solution -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.
