How many electrons maximum can have n+l = 4 in an atom.

Options

A. 8
B. 2
C. 6
D. 18

Answer

To determine how many electrons can have \( n + l = 4 \) in an atom, we will follow these steps:

### Step 1: Understand the \( n + l \) Rule
The quantum numbers \( n \) and \( l \) are used to describe the energy levels and sublevels of electrons in an atom. The principal quantum number \( n \) indicates the main energy level, while the azimuthal quantum number \( l \) indicates the shape of the orbital.

### Step 2: Identify Possible Combinations of \( n \) and \( l \)
Given that \( n + l = 4 \), we need to find all possible combinations of \( n \) and \( l \) that satisfy this equation.

1. **Combination 1:**
- Let \( n = 3 \)
- Then \( l = 4 - n = 4 - 3 = 1 \)
- This corresponds to the 3p subshell.

2. **Combination 2:**
- Let \( n = 4 \)
- Then \( l = 4 - n = 4 - 4 = 0 \)
- This corresponds to the 4s subshell.

### Step 3: Determine the Maximum Number of Electrons in Each Subshell
Now we will find out how many electrons can be accommodated in each of the identified subshells.

1. **For the 3p subshell:**
- The maximum number of electrons that can occupy a p subshell is 6.

2. **For the 4s subshell:**
- The maximum number of electrons that can occupy an s subshell is 2.

### Step 4: Calculate the Total Maximum Electrons
Now, we add the maximum number of electrons from both subshells:

\[ \text{Total electrons} = \text{Electrons in 3p} + \text{Electrons in 4s} = 6 + 2 = 8 \]

### Conclusion
The maximum number of electrons that can have \( n + l = 4 \) in an atom is **8 electrons**.

---