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Multiple Choice
How many valence electrons does an atom of aluminum (Al) have?
A
1
B
2
C
3
D
5
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.
Determine the electron configuration of aluminum by filling the orbitals in order: 1s, 2s, 2p, 3s, and 3p.
Write the electron configuration for aluminum: $1s^2 2s^2 2p^6 3s^2 3p^1$.
Recognize that valence electrons are the electrons in the outermost shell (highest principal quantum number, n). For aluminum, this is the third shell (3s and 3p orbitals).
Count the electrons in the 3s and 3p orbitals: $3s^2$ has 2 electrons and $3p^1$ has 1 electron, so aluminum has a total of 3 valence electrons.