Step 1: Understanding Polarizability
Polarizability describes an ion or atom's capacity for its electron cloud to be distorted by an external electric field. Generally, larger ions with more electrons exhibit higher polarizability.
Step 2: Analyzing Halide Ions
The halide ions are \( \text{F}^- \), \( \text{Cl}^- \), \( \text{Br}^- \), and \( \text{I}^- \). Their polarizability increases proportionally with their size and electron count.
Step 3: Order of Polarizability
The polarizability order for halide ions is as follows:\[\text{F}^-<\text{Cl}^-<\text{Br}^-<\text{I}^-.\]
This progression is due to \( \text{I}^- \) being the largest and possessing the most electrons, rendering it the most polarizable, while \( \text{F}^- \) is the smallest and least polarizable.
Step 4: Matching with the Options
The established order \( \text{F}^-<\text{Cl}^-<\text{Br}^-<\text{I}^- \) aligns with option (D).Final Answer: The polarizability of halide ions exhibits an increasing trend in the sequence \( \text{F}^-<\text{Cl}^-<\text{Br}^-<\text{I}^- \).