In iron atom, how many electrons have n=3 and l=2?

Options

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

Answer

To determine how many electrons in an iron atom have the principal quantum number \( n = 3 \) and the azimuthal quantum number \( l = 2 \), we can follow these steps:

### Step 1: Identify the atomic number of iron
Iron has an atomic number of 26. This means it has 26 electrons.

### Step 2: Write the electronic configuration of iron
The electronic configuration of iron can be derived from the noble gas configuration. The configuration is:
\[ \text{[Ar]} \, 3d^6 \, 4s^2 \]
This indicates that iron has 18 electrons in the configuration of argon, 6 electrons in the 3d subshell, and 2 electrons in the 4s subshell.

### Step 3: Understand the quantum numbers
- The principal quantum number \( n \) indicates the shell level of the electron. For \( n = 3 \), we are looking at the third shell.
- The azimuthal quantum number \( l \) indicates the type of subshell. For \( l = 2 \), this corresponds to the d subshell.

### Step 4: Identify the relevant electrons
In the electronic configuration \( 3d^6 \):
- The \( 3d \) subshell corresponds to \( n = 3 \) and \( l = 2 \).
- The \( 3d \) subshell contains 6 electrons.

### Conclusion
Thus, the number of electrons in an iron atom that have \( n = 3 \) and \( l = 2 \) is **6**.