How many electron in Al (Z =13) have n = 3, l = 1 ?

Options

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

Explanation

To determine how many electrons in aluminum (Al) with atomic number Z = 13 have the principal quantum number n = 3 and azimuthal quantum number l = 1, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Atomic Number**:
- The atomic number of aluminum (Al) is 13. This means aluminum has 13 electrons.

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

3. **Identify the Relevant Quantum Numbers**:
- We are interested in electrons with:
- Principal quantum number (n) = 3
- Azimuthal quantum number (l) = 1
- The value of l = 1 corresponds to the p orbitals.

4. **Locate the Electrons in the Relevant Orbitals**:
- From the electronic configuration, we look at the electrons in the n = 3 shell:
- 3s² (2 electrons)
- 3p¹ (1 electron)
- Therefore, the total number of electrons in the n = 3 shell is 2 (from 3s) + 1 (from 3p) = 3 electrons.

5. **Determine the Electrons in the 3p Orbital**:
- Since we are specifically looking for electrons where n = 3 and l = 1, we focus on the 3p orbital.
- From the configuration, we see that there is 1 electron in the 3p orbital.

### Final Answer:
- There is **1 electron** in aluminum (Al) with n = 3 and l = 1.

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