On the periodic table, aluminium is the period 3 element with three valence electrons.
Aluminium, spelled aluminum in American English, has atomic number 13 and the symbol Al. Its electron arrangement is [Ne] 3s² 3p¹, so three electrons occupy its outermost shell. It appears in group 13 and period 3.
Aluminium is a relatively light, silvery metal that forms a thin protective oxide layer in air. This passivation helps it resist corrosion. The metal is widely used in transport, construction, packaging, electrical equipment, and household products because it combines low density with useful strength and conductivity.
The spelling difference is not a difference in element identity: aluminium is the official IUPAC spelling, while aluminum is common in the United States. Aluminium is also easily confused with silicon, the next element in period 3, which has four valence electrons rather than three.