Aluminum is an element of periodic table and is symbol is Al. Aluminum is a poor metal and it is grey in color. The atomic number and atomic mass of aluminum is 13 and 20.98 grams per mole respectively. There are 13 electrons present in an atom of aluminum. The numbers of electrons per shell of aluminum is 2, 8, 3. The electronic configuration of aluminum is 3s2 3p1. The valence electrons in aluminum atom are filled in p-orbital so, aluminum is present in p-block of periodic table. It has three electrons in outer most shell therefore, it is placed in 3(A) group of periodic table. Moreover, the period number of aluminum is 3 because it has three energy levels filled with electrons.