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 bond between two atoms has ionic properties, while covalent character refers to the extent to which a bond has covalent properties. According to Fajan's rule, the covalent character is inversely proportional to ionic character.

### Step 2: Analyze the Cations
- In this case, the anion (H⁻) is the same for all hydrides. Therefore, we only need to focus on the cations: Li⁺, Na⁺, K⁺, Rb⁺, and Cs⁺.

### Step 3: Apply Fajan's Rule
- Fajan's rule states that the larger the cation, the more ionic the compound will be. This is because larger cations have a lower charge density, which leads to less polarization of the anion.

### Step 4: Determine the Size of the Cations
- The order of the size of the cations from smallest to largest is:
- Li⁺ < Na⁺ < K⁺ < Rb⁺ < Cs⁺
- Therefore, Cs⁺ is the largest cation, and Li⁺ is the smallest.

### Step 5: Establish the Order of Ionic Character
- Since larger cations lead to more ionic character, the order of increasing ionic character for the hydrides is:
- LiH < NaH < KH < RbH < CsH

### Conclusion
- The correct order of increasing ionic character among the metal hydrides is:
- LiH < NaH < KH < RbH < CsH

### Final Answer
- The correct order of increasing ionic character is: **LiH < NaH < KH < RbH < CsH**

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