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Magnesium is an alkaline earth metal with an atomic number of 12. It is in the third row of the periodic table. Which expression shows one way to find the number of valence electrons in one atom of magnesium?

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]

Sagot :

GinnyAnsweridn
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]
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