How many electrons are present in the M shell of an atom of an element with atomic number 23?

Options

A. 5
B. 6
C. 12
D. 11

Explanation

To determine how many electrons are present in the M shell of an atom with atomic number 23, we can follow these steps:

### Step 1: Identify the atomic number
The atomic number of the element is given as 23. This means the element has 23 protons and, in a neutral atom, also 23 electrons.

### Step 2: Write the electronic configuration
To find out how the electrons are distributed among the shells, we need to write the electronic configuration of the element with atomic number 23. The electronic configuration is filled according to the Aufbau principle, which states that electrons occupy the lowest energy orbitals first.

The electronic configuration for atomic number 23 (which corresponds to the element Vanadium) is:
- 1s² 2s² 2p⁶ 3s² 3p⁶ 3d³

### Step 3: Identify the shells and their corresponding subshells
The shells are designated as follows:
- K shell (n=1): 1s
- L shell (n=2): 2s, 2p
- M shell (n=3): 3s, 3p, 3d

### Step 4: Count the electrons in the M shell
Now, we need to count the electrons in the M shell (n=3). The subshells in the M shell are:
- 3s²: 2 electrons
- 3p⁶: 6 electrons
- 3d³: 3 electrons

Now, we add these electrons together:
- Total electrons in M shell = 2 (from 3s) + 6 (from 3p) + 3 (from 3d) = 11 electrons.

### Step 5: Conclusion
Thus, the total number of electrons present in the M shell of an atom with atomic number 23 is **11**.

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