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

Options

A. 5
B. 6
C. 7
D. 4

Explanation

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

### Step 1: Identify the Electron Configuration
The atom has:
- 2 electrons in the K shell (1st shell)
- 8 electrons in the L shell (2nd shell)
- 5 electrons in the M shell (3rd shell)

### Step 2: Write the Electronic Configuration
We can write the electronic configuration based on the distribution of electrons in the shells:
- K shell: 2 electrons → 1s²
- L shell: 8 electrons → 2s² 2p⁶
- M shell: 5 electrons → 3s² 3p³

So, the complete electronic configuration is:
\[ 1s^2 \, 2s^2 \, 2p^6 \, 3s^2 \, 3p^3 \]

### Step 3: Count the Total Number of Electrons
Now, let's verify the total number of electrons:
- K shell: 2
- L shell: 8
- M shell: 5

Total = 2 + 8 + 5 = 15 electrons. This confirms our configuration is correct.

### Step 4: Identify the Valence Shell
The valence shell is the shell with the highest principal quantum number (n). Here, the highest n value is 3 (M shell).

### Step 5: Count the Electrons in the Valence Shell
In the M shell (n=3), we have:
- 3s: 2 electrons
- 3p: 3 electrons

Total electrons in the valence shell = 2 (from 3s) + 3 (from 3p) = 5 electrons.

### Conclusion
The number of electrons in the valence shell is **5**.

---