Question

Which is the weakest ligand?

• A. \( \text{F}^- \)
• B. \text{EDTA}
• C. \text{en}
• D. \text{CO}

Hint:

To identify weak and strong ligands, remember that halide ions like \( \text{F}^- \) are typically weaker, while chelating agents like EDTA and \( \text{CO} \) are among the strongest.

Answer 1

The Correct Option is A

Ligands are species that bind to a central metal atom or ion in a complex. The strength of a ligand is determined by its ability to donate electron pairs to the metal center. Ligands can be classified as strong or weak field ligands based on their ability to split the d-orbitals of the metal ion. - \( \text{F}^- \) (Fluoride ion): \( \text{F}^- \) is a weak field ligand. It is a halide ion and has a lower ability to split the d-orbitals of the metal ion. - EDTA (Ethylenediaminetetraacetate): EDTA is a strong field ligand. It is a chelating ligand and binds to the metal center through multiple donor atoms, which makes it a strong ligand. - en (Ethylenediamine): en is a bidentate ligand, meaning it can donate two lone pairs to the metal. It is also a strong field ligand, though not as strong as EDTA. - CO (Carbon monoxide): CO is a very strong field ligand. It binds strongly to the metal center through its lone pair and is known for forming very stable metal complexes.
Step 1: Conclusion Since fluoride (\( \text{F}^- \)) is the weakest among the given ligands in terms of its ability to split the metal’s d-orbitals, the correct answer is \( \boxed{\text{F}^-} \).