Dihydrogen form three types of hydrides. (i)___ hydrides are formed by alkali metals and alkaline earth metals. (ii)___ hydrides are formed by non-metals and (iii)___ hydrides are formed by d abd f-block elements at elevated temperature. Complex metal hydrides such as (iv)___ and (v)___ are powerful reducing agents.

Answer

To solve the question regarding the types of hydrides formed by dihydrogen, we can break it down into the three types of hydrides and the complex metal hydrides mentioned in the question.

### Step-by-Step Solution:

1. **Identify the first type of hydride**:
- Dihydrogen forms hydrides with alkali metals and alkaline earth metals. These hydrides are characterized by ionic bonding due to the high electronegativity difference between hydrogen and these metals.
- **Answer**: Ionic hydrides.

2. **Identify the second type of hydride**:
- Dihydrogen also forms hydrides with non-metals. These hydrides typically involve covalent bonding, where hydrogen shares electrons with non-metals.
- **Answer**: Covalent hydrides.

3. **Identify the third type of hydride**:
- Dihydrogen can form hydrides with d-block and f-block elements at elevated temperatures. These hydrides are often referred to as interstitial hydrides, where hydrogen atoms occupy interstitial sites in the metal lattice.
- **Answer**: Interstitial hydrides.

4. **Identify the complex metal hydrides**:
- Complex metal hydrides are formed from combinations of metals and hydride ions. Two well-known examples of complex metal hydrides that act as powerful reducing agents are lithium aluminum hydride and sodium borohydride.
- **Answer**: Lithium aluminum hydride (LiAlH4) and sodium borohydride (NaBH4).

### Final Answers:
(i) Ionic hydrides
(ii) Covalent hydrides
(iii) Interstitial hydrides
(iv) Lithium aluminum hydride (LiAlH4)
(v) Sodium borohydride (NaBH4)