A neutral atom of an element has `2K,8L` and `5M` electron .Find out the following
Number of unpaired electrons

Options

A. 2
B. 3
C. 4
D. 5

Explanation

To find the number of unpaired electrons in a neutral atom with the given electron configuration of `2K, 8L, and 5M`, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Electron Configuration**:
- The atom has 2 electrons in the K shell, 8 electrons in the L shell, and 5 electrons in the M shell.
- This gives us a total of \(2 + 8 + 5 = 15\) electrons.

2. **Write the Electronic Configuration**:
- The electronic configuration of the atom can be written as:
- K shell: \(1s^2\) (2 electrons)
- L shell: \(2s^2, 2p^6\) (8 electrons)
- M shell: \(3s^2, 3p^3\) (5 electrons)
- Therefore, the complete electronic configuration is \(1s^2, 2s^2, 2p^6, 3s^2, 3p^3\).

3. **Identify the Outermost Shell**:
- The outermost shell is the M shell (n=3), which contains the electrons \(3s^2\) and \(3p^3\).

4. **Determine the Electron Distribution in the M Shell**:
- In the \(3s\) subshell, there are 2 electrons, which are paired.
- In the \(3p\) subshell, there are 3 electrons. The \(3p\) subshell can hold a maximum of 6 electrons, distributed in three orbitals (each can hold 2 electrons).
- The distribution of the 3 electrons in the \(3p\) subshell will be:
- One electron in each of the three \(3p\) orbitals (due to Hund's rule), resulting in all 3 being unpaired.

5. **Count the Number of Unpaired Electrons**:
- From the \(3s\) subshell, there are 0 unpaired electrons (2 paired).
- From the \(3p\) subshell, there are 3 unpaired electrons (1 in each of the three orbitals).
- Therefore, the total number of unpaired electrons is \(0 + 3 = 3\).

### Final Answer:
The number of unpaired electrons in the atom is **3**.

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