How many electron in Na (Z =11) have n = 2, l = 0 ?

Options

A. 2
B. 4
C. 1
D. 3

Explanation

To determine how many electrons in sodium (Na) with atomic number Z = 11 have quantum numbers n = 2 and l = 0, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Electron Configuration of Sodium (Na)**:
- Sodium has an atomic number of 11, which means it has 11 electrons.
- The electron configuration of sodium is:
\[ 1s^2 \, 2s^2 \, 2p^6 \, 3s^1 \]

2. **Understand the Quantum Numbers**:
- The principal quantum number \( n \) indicates the energy level of the electron.
- The azimuthal quantum number \( l \) indicates the subshell (orbital type). For \( l = 0 \), the subshell is the s orbital.

3. **Identify the Relevant Electrons**:
- We are looking for electrons with \( n = 2 \) and \( l = 0 \).
- The only subshell that corresponds to \( l = 0 \) is the 2s subshell.

4. **Count the Electrons in the 2s Orbital**:
- From the electron configuration, we see that the 2s orbital has:
\[ 2s^2 \]
- This means there are 2 electrons in the 2s orbital.

5. **Conclusion**:
- Therefore, the number of electrons in sodium (Na) with quantum numbers \( n = 2 \) and \( l = 0 \) is **2**.

### Final Answer:
The number of electrons in Na (Z = 11) with \( n = 2 \) and \( l = 0 \) is **2**.