Aluminum (symbol: Al) has an atomic number of 13, indicating that it has 13 electrons in total. When determining the number of valence electrons in an atom, we focus on the outermost electron shell, also known as the valence shell.
In the case of aluminum, the electron configuration is 1s² 2s² 2p⁶ 3s² 3p¹, following the Aufbau principle. The first and second electron shells (1s and 2s) are fully filled with 2 electrons each, while the 2p subshell is filled with 6 electrons. The valence shell, 3s² 3p¹, has 3 electrons in total. Therefore, aluminum has three valence electrons.
Valence electrons are involved in the chemical bonding and interactions of atoms with other atoms. Although aluminum has only three valence electrons, it is still capable of forming various chemical bonds and compounds due to its ability to donate or share these electrons.