number of electrons present in M shell of an element with atomic number 26 in its `M^(3+)` state will be

Options

A. zero
B. 8
C. 13
D. 14

Answer

To determine the number of electrons present in the M shell of an element with atomic number 26 in its \( M^{3+} \) state, we can follow these steps:

### Step 1: Determine the electron configuration of the element
The element with atomic number 26 is iron (Fe). The electron configuration of iron is:
\[ 1s^2 \, 2s^2 \, 2p^6 \, 3s^2 \, 3p^6 \, 4s^2 \, 3d^6 \]

### Step 2: Identify the oxidation state
In the \( M^{3+} \) state, we need to remove 3 electrons from the neutral atom. The electrons are removed from the outermost shells first.

### Step 3: Remove electrons from the electron configuration
When we remove 3 electrons from the electron configuration of iron, we typically remove them from the 4s and 3d subshells. The removal sequence is as follows:
- Remove 2 electrons from the \( 4s^2 \) subshell.
- Remove 1 electron from the \( 3d^6 \) subshell.

After removing these electrons, the new electron configuration will be:
\[ 1s^2 \, 2s^2 \, 2p^6 \, 3s^2 \, 3p^6 \, 3d^5 \]

### Step 4: Identify the electrons in the M shell
The M shell corresponds to the principal quantum number \( n = 3 \). The electrons in the M shell come from the \( 3s \), \( 3p \), and \( 3d \) subshells.

Counting the electrons:
- From \( 3s^2 \): 2 electrons
- From \( 3p^6 \): 6 electrons
- From \( 3d^5 \): 5 electrons

Total electrons in the M shell:
\[ 2 + 6 + 5 = 13 \]

### Conclusion
The number of electrons present in the M shell of the element with atomic number 26 in its \( M^{3+} \) state is **13**.

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