Give two examples of intrinsic semiconductor?

Answer

### Step-by-Step Solution:

1. **Definition of Intrinsic Semiconductor**:
An intrinsic semiconductor is a pure semiconductor material that has no significant dopant species present. It is characterized by having equal numbers of holes (positive charge carriers) and free electrons (negative charge carriers).

2. **Valency of Elements**:
Intrinsic semiconductors typically have a valency of four. This means that each atom can form four covalent bonds with neighboring atoms, allowing for the formation of a crystal lattice structure.

3. **Examples of Intrinsic Semiconductors**:
- **Germanium (Ge)**:
- Atomic Number: 32
- It is a widely used intrinsic semiconductor material due to its suitable energy band gap and electrical properties.
- **Silicon (Si)**:
- Atomic Number: 14
- Silicon is the most commonly used intrinsic semiconductor in electronic devices, especially in integrated circuits and solar cells.
- **Carbon (C)**:
- Atomic Number: 6
- In its diamond form, carbon can also act as an intrinsic semiconductor due to its four valence electrons.

4. **Key Characteristics**:
- In intrinsic semiconductors, the number of holes is equal to the number of free electrons, which is an important property that distinguishes them from extrinsic semiconductors (which are doped with impurities).

### Final Answer:
Two examples of intrinsic semiconductors are:
1. Germanium (Ge)
2. Silicon (Si)