When an alkali metal is reacted with hydrogen then metallic hydride is formed. In this reaction

Options

A. Hydrogen is oxidised
B. Hydrogen is reduced
C. Hydrogen is neither oxidised nor reduced
D. Hydrogen is oxidised as well as reduced

Answer

To solve the question regarding the reaction between an alkali metal and hydrogen to form a metallic hydride, we can follow these steps:

### Step 1: Identify the Reactants and Products
When an alkali metal (such as Lithium, Sodium, or Potassium) reacts with hydrogen (H₂), the product formed is a metallic hydride (MH, where M represents the alkali metal).

### Step 2: Determine the Oxidation States
- In elemental hydrogen (H₂), the oxidation state of hydrogen is 0.
- In the metallic hydride (MH), the oxidation state of hydrogen is -1.

### Step 3: Analyze the Change in Oxidation States
- The alkali metal (M) starts with an oxidation state of 0 in its elemental form and ends up with a positive oxidation state (usually +1 for alkali metals in hydrides).
- Hydrogen, on the other hand, is reduced from an oxidation state of 0 to -1.

### Step 4: Identify the Type of Reaction
Since hydrogen is going from 0 to -1, it is gaining electrons, which means it is being reduced. Therefore, the alkali metal is oxidized (losing electrons) while hydrogen is reduced.

### Step 5: Conclusion
In this reaction, hydrogen is reduced. The correct answer to the question is that hydrogen is reduced.

### Final Answer:
Hydrogen is reduced when an alkali metal reacts with hydrogen to form a metallic hydride.

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