In how many elements the last electron will have the following set of quantum numbers, n = 3 and l = 1?

Options

A. 2
B. 8
C. 6
D. 10

Explanation

To determine how many elements have their last electron characterized by the quantum numbers \( n = 3 \) and \( l = 1 \), we can follow these steps:

### Step 1: Understand the Quantum Numbers
The principal quantum number \( n \) indicates the energy level of the electron, while the azimuthal quantum number \( l \) indicates the subshell. For \( l = 1 \), the corresponding subshell is the \( p \) subshell.

### Step 2: Identify the Subshell
Given \( n = 3 \) and \( l = 1 \), we are referring to the 3p subshell. The 3p subshell can hold a maximum of 6 electrons, as each p subshell has three orbitals (3p_x, 3p_y, 3p_z), and each orbital can hold 2 electrons.

### Step 3: Determine the Elements
The elements that have their last electron in the 3p subshell are those in the range of atomic numbers that fill this subshell. The filling of the 3p subshell starts after the 3s subshell is filled. The relevant elements are:

- **Aluminum (Al)** - Atomic number 13
- **Silicon (Si)** - Atomic number 14
- **Phosphorus (P)** - Atomic number 15
- **Sulfur (S)** - Atomic number 16
- **Chlorine (Cl)** - Atomic number 17
- **Argon (Ar)** - Atomic number 18

### Step 4: Count the Elements
From the list above, we can see that there are 6 elements (Al, Si, P, S, Cl, Ar) whose last electron occupies the 3p subshell.

### Conclusion
Thus, the answer to the question is that there are **6 elements** whose last electron has the quantum numbers \( n = 3 \) and \( l = 1 \).

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