`AsF_5` reacts with `XeF_4` to form an adduct. The shapes of cation and anion in the adduct are respectively.

Options

A. square planar, octahedral
B. T-shaped, octahedral
C. square pyramidal, octahedral
D. square planar, trigonal bipyramidal

Answer

To determine the shapes of the cation and anion formed when AsF5 reacts with XeF4, we can follow these steps:

### Step 1: Identify the Products of the Reaction
When AsF5 reacts with XeF4, it forms an adduct consisting of a cation and an anion. The cation is XeF3^+ and the anion is AsF6^-.

### Step 2: Determine the Shape of the Cation (XeF3^+)
- **Valence Shell Electron Pair Repulsion (VSEPR) Theory**: To find the shape of XeF3^+, we need to consider the number of bonding pairs and lone pairs around the central atom (Xenon).
- **Xenon (Xe)** has 8 valence electrons. In XeF3^+, it forms 3 bonds with fluorine atoms, using 3 of its valence electrons.
- Since it has a positive charge, it effectively has one less electron, leaving it with 4 electrons (8 - 3 - 1 = 4).
- These 4 electrons will form 2 lone pairs.
- The arrangement of 3 bonding pairs and 2 lone pairs leads to a T-shaped geometry.

### Step 3: Determine the Shape of the Anion (AsF6^-)
- **For AsF6^-**, we again apply VSEPR theory.
- **Arsenic (As)** has 5 valence electrons. In AsF6^-, it forms 6 bonds with fluorine atoms, using all 5 of its valence electrons and one additional electron from the negative charge.
- This results in 6 bonding pairs and no lone pairs.
- The arrangement of 6 bonding pairs leads to an octahedral geometry.

### Conclusion
- The shape of the cation (XeF3^+) is T-shaped.
- The shape of the anion (AsF6^-) is octahedral.

### Final Answer
The shapes of the cation and anion in the adduct are respectively T-shaped and octahedral.

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