How many valence electrons does an atom of aluminum (Al) have?

• A. 2
• B. 4
• C. 1
• D. 3

Answer: (D)

Verified step by step guidance

1. Identify the atomic number of aluminum (Al), which is 13. This tells us the total number of electrons in a neutral atom of aluminum.
2. Write the electron configuration of aluminum to understand the distribution of electrons in its shells: \$1s^2 2s^2 2p^6 3s^2 3p^1$.
3. Recognize that valence electrons are the electrons in the outermost shell (highest principal quantum number). For aluminum, the outermost shell is the third shell (n=3).
4. Count the electrons in the third shell: \$3s^2\( and \)3p^1\( add up to \)2 + 1 = 3$ valence electrons.
5. Conclude that an atom of aluminum has 3 valence electrons based on its electron configuration.