Which one of the following alternatives contains molecules and ions that are all likely to form a complex ion with a transition metal cation? A - VCE - SSCE Chemistry - Question 5 - 2007 - Paper 1

To assess which alternative contains species likely to form complex ions with transition metal cations, we need to consider the ligand properties of the molecules and ions listed:

1. NH₃ (ammonia) is a well-known ligand that can donate a lone pair of electrons to form coordinate bonds with transition metal ions.

2. Cl^- (chloride ion) can act as a ligand, though it is a weaker field ligand compared to others like CN^- and NH₃.

3. F^- (fluoride ion) is also a relatively weak ligand, but it can still form complexes with certain transition metals.

4. H₂O (water) is a common ligand, often forming complexes, especially with transition metals like Cu²⁺ and Ag⁺.

In contrast, the other options include species such as CH₄, which cannot act as a ligand, and Na⁺, which is a cation and cannot coordinate similarly. Thus, option B is the best choice for ligands that effectively form complex ions with transition metals.