How many valence electrons are present in Mg?

Options

A. 1
B. 2
C. 3
D. 4

Explanation

To determine the number of valence electrons in magnesium (Mg), we can follow these steps:

### Step 1: Identify the Atomic Number
The atomic number of magnesium (Mg) is 12. This means that a neutral magnesium atom has 12 electrons.

### Step 2: Write the Electronic Configuration
We need to write the electronic configuration of magnesium to find out how the electrons are distributed in the various energy levels (shells). The order of filling the orbitals is as follows:
1. 1s
2. 2s
3. 2p
4. 3s
5. 3p
6. 4s
7. 3d
8. 4p

For magnesium (atomic number 12), the electronic configuration is:
- 1s² (2 electrons)
- 2s² (2 electrons)
- 2p⁶ (6 electrons)
- 3s² (2 electrons)

So, the complete electronic configuration is: **1s² 2s² 2p⁶ 3s²**.

### Step 3: Identify the Valence Electrons
Valence electrons are the electrons present in the outermost shell of an atom. For magnesium, the outermost shell is the third shell, which contains the 3s orbital.

From the electronic configuration:
- The outermost shell (n=3) has 2 electrons in the 3s orbital.

### Conclusion
Thus, magnesium has **2 valence electrons**.

### Final Answer
The number of valence electrons in magnesium (Mg) is **2**.

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