Aluminum has an atomic number of 13, which means it has 13 protons and, in a neutral atom, also 13 electrons. The electron configuration of aluminum is \(1s^2 2s^2 2p^6 3s^2 3p^1\).
The valence electrons are the electrons in the outermost shell (the highest principal quantum number). In the case of aluminum, the outermost shell is the third shell (n=3), which contains 2 electrons in the 3s subshell and 1 electron in the 3p subshell.
So, aluminum has a total of 3 valence electrons (2 from the 3s subshell and 1 from the 3p subshell).
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