To determine the number of valence electrons in an atom of magnesium, we need to consider its position in the periodic table. Here's the step-by-step solution:
1. Identify the Group Number:
Magnesium is an alkaline earth metal, which places it in Group 2 of the periodic table. Elements in Group 2 have two valence electrons.
2. Recognize the Provided Expressions:
The given options are:
- A. [tex]\( 12 \times 3 \)[/tex]
- B. [tex]\( 12 + 3 \)[/tex]
- C. [tex]\( (12 - 8) - 2 \)[/tex]
- D. [tex]\( (12 - 2) + 8 \)[/tex]
- E. [tex]\( (12 + 2) - 8 \)[/tex]
3. Analyze the Expressions:
- Option A: [tex]\( 12 \times 3 = 36 \)[/tex]
- Option B: [tex]\( 12 + 3 = 15 \)[/tex]
- Option C: [tex]\( (12 - 8) - 2 = 4 - 2 = 2 \)[/tex]
- Option D: [tex]\( (12 - 2) + 8 = 10 + 8 = 18 \)[/tex]
- Option E: [tex]\( (12 + 2) - 8 = 14 - 8 = 6 \)[/tex]
4. Select the Correct Expression:
The expression that matches the correct number of valence electrons is option C, as it yields the result that an atom of magnesium has 2 valence electrons.
Therefore, the correct expression is:
C. [tex]\( (12 - 8) - 2 \)[/tex]
