Metal hydrides are ionic, covalent or molecular in nature. Among LiH, NaH, KH, RbH, CsH the correct order of increasing ionic character is

Options

A. `LiH gt NAH gt CsH gt KH gt RbH`
B. `LiH lt NaH lt KH lt RbH lt CsH`
C. `RbH gt CsH gt NaH gt KH gt LiH`
D. `NaH gt CsH gt RbH gt LiH gt KH`

Explanation

To determine the correct order of increasing ionic character among the metal hydrides LiH, NaH, KH, RbH, and CsH, we can follow these steps:

### Step 1: Understand Ionic and Covalent Character
Ionic character refers to the extent to which a compound exhibits ionic properties, while covalent character refers to the extent to which a compound exhibits covalent properties. According to Fajans' rules, the ionic character of a compound is inversely related to its covalent character.

### Step 2: Analyze the Cation Sizes
The ionic character of these metal hydrides is influenced by the size of the cations (Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺). As the size of the cation increases, the covalent character increases, and consequently, the ionic character decreases.

- **Li⁺** (smallest cation)
- **Na⁺**
- **K⁺**
- **Rb⁺**
- **Cs⁺** (largest cation)

### Step 3: Determine the Order of Cation Size
The order of cation size from smallest to largest is:
- Li⁺ < Na⁺ < K⁺ < Rb⁺ < Cs⁺

### Step 4: Relate Cation Size to Ionic Character
Since ionic character is inversely proportional to the size of the cation:
- Smaller cations (like Li⁺) will have higher ionic character.
- Larger cations (like Cs⁺) will have lower ionic character.

### Step 5: Establish the Order of Increasing Ionic Character
Based on the cation sizes, we can establish the order of increasing ionic character as follows:
- CsH (least ionic character)
- RbH
- KH
- NaH
- LiH (most ionic character)

### Final Order
Thus, the correct order of increasing ionic character among the given metal hydrides is:
**CsH < RbH < KH < NaH < LiH**