Aluminum, which is represented by the symbol Al on the periodic table, has 13 electrons. This is because the atomic number of aluminum is 13, and the atomic number indicates the number of protons in an atom, which is equal to the number of electrons in a neutral atom.
To put it simply, in order for an atom to be electrically neutral, it needs to have the same number of positively charged protons as negatively charged electrons. Since aluminum has an atomic number of 13, it possesses 13 protons in its nucleus and, therefore, also has 13 electrons orbiting around it.