What do you understand by the term 'non-stoichiometric hydrides' ? Do you expect this type of hydrides to be formed by alkali metals'? Justify your answer.

Explanation

### Step-by-Step Solution:

1. **Definition of Non-Stoichiometric Hydrides**:
Non-stoichiometric hydrides, also known as interstitial hydrides or metallic hydrides, are compounds formed by hydrogen and metals, where the ratio of metal to hydrogen is not fixed. This means that the composition can vary, and the hydrides can exist in forms that do not adhere to the law of constant composition.

2. **Formation of Non-Stoichiometric Hydrides**:
These hydrides are typically formed by transition metals, lanthanides, and actinides. In these cases, hydrogen atoms occupy the interstitial sites within the metal lattice structure. The general formula for these hydrides can be represented as MₓHₓ, where M is the metal and x can be a fraction or decimal, indicating the variable ratio of metal to hydrogen.

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