The number of electrons in the valence shell of calcium is:

Options

A. 2
B. 4
C. 6
D. 8

Explanation

To find the number of electrons in the valence shell of calcium, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Atomic Number of Calcium**:
- Calcium has an atomic number (Z) of 20. This means it has 20 electrons.

2. **Write the Electronic Configuration**:
- The electronic configuration of calcium can be written as:
\[ 1s^2 \, 2s^2 \, 2p^6 \, 3s^2 \, 3p^6 \, 4s^2 \]
- This configuration shows how the 20 electrons are distributed among the various atomic orbitals.

3. **Determine the Valence Shell**:
- The valence shell is defined as the outermost shell of an atom. We identify the outermost shell by looking for the highest principal quantum number (n).
- In the electronic configuration, the highest principal quantum number is 4 (from the 4s orbital).

4. **Count the Electrons in the Valence Shell**:
- In the 4s orbital, there are 2 electrons. Therefore, the total number of electrons in the valence shell of calcium is:
\[ \text{Number of valence electrons} = 2 \]

5. **Conclusion**:
- The number of electrons in the valence shell of calcium is **2**.

### Final Answer:
The number of electrons in the valence shell of calcium is **2**.

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