A neutral atom of magnesium (Mg) has 12 electrons. Identify the number of valence electrons.

1. ### Break Down the Problem

To determine the number of valence electrons in a neutral atom of magnesium (Mg), we need to understand its electron configuration and identify the outermost shell of electrons.

2. ### Relevant Concepts

Magnesium (Mg) has an atomic number of 12, which means it has 12 electrons. The electron configuration of magnesium can be represented as: $\text{Mg: } 1s^2 2s^2 2p^6 3s^2$ To find the valence electrons, we focus on the electrons in the outermost shell. In this case, the outermost shell is the third energy level.

3. ### Analysis and Detail

1. The electron configuration shows:

   • The first shell (1s) has 2 electrons.
   • The second shell (2s and 2p) has a total of 8 electrons (2 in 2s and 6 in 2p).
   • The third shell (3s) has 2 electrons.

2. Valence electrons are the electrons found in the outermost shell, which for magnesium is the 3rd shell.

4. ### Verify and Summarize

The outermost shell (3s) of magnesium has 2 electrons. Therefore, the number of valence electrons in a neutral magnesium atom is:

Final Answer

2 valence electrons.