How many electron in Al (Z =13) have n = 3, l = 0 ?

Options

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

Answer

To determine how many electrons in aluminum (Al) with atomic number Z = 13 have quantum numbers n = 3 and l = 0, we will follow these steps:

### Step-by-Step Solution:

1. **Identify the Atomic Number**:
Aluminum has an atomic number of 13, which means it has 13 electrons.

2. **Write the Electronic Configuration**:
The electronic configuration of aluminum can be written as:
- 1s² 2s² 2p⁶ 3s² 3p¹
This configuration shows how the 13 electrons are distributed among the various orbitals.

3. **Understand Quantum Numbers**:
The quantum number n (principal quantum number) indicates the energy level of the electron, while l (azimuthal quantum number) indicates the type of orbital:
- l = 0 corresponds to the s orbital.

4. **Identify the Relevant Orbital**:
For n = 3 and l = 0, we are looking at the 3s orbital.

5. **Count the Electrons in the 3s Orbital**:
From the electronic configuration, we see that the 3s orbital has 2 electrons (3s²).

6. **Conclusion**:
Therefore, the number of electrons in aluminum that have n = 3 and l = 0 is **2**.

### Final Answer:
There are **2 electrons** in Al (Z = 13) that have n = 3 and l = 0.

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