The number of electrons in the M-shell of the element with atomic number 19 is :-

Options

A. 1
B. 8
C. 10
D. 6

Explanation

To determine the number of electrons in the M-shell of the element with atomic number 19, we can follow these steps:

### Step 1: Identify the Element
The element with atomic number 19 is potassium (K).

### Step 2: Write the Electronic Configuration
The electronic configuration of potassium (K) can be written as:
\[ \text{K: } 1s^2, 2s^2, 2p^6, 3s^2, 3p^6, 4s^1 \]

### Step 3: Determine the Shells
In the electronic configuration:
- The **K-shell** (1st shell) can hold a maximum of 2 electrons: \(1s^2\)
- The **L-shell** (2nd shell) can hold a maximum of 8 electrons: \(2s^2, 2p^6\)
- The **M-shell** (3rd shell) can hold a maximum of 18 electrons: \(3s^2, 3p^6\)
- The **N-shell** (4th shell) can hold more, but for potassium, we only have \(4s^1\)

### Step 4: Count the Electrons in the M-shell
From the electronic configuration:
- The M-shell consists of the electrons in the 3s and 3p subshells.
- From the configuration, we see that there are \(3s^2\) (2 electrons) and \(3p^6\) (6 electrons) in the M-shell.

Thus, the total number of electrons in the M-shell is:
\[ 2 + 6 = 8 \]

### Conclusion
The number of electrons in the M-shell of potassium (atomic number 19) is **8**.

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