Simply put, the external electron configuration of aluminum atoms is 2, 8, 3.
The number of electrons in the outermost shell is not enough, and the structure is unstable. Three electrons are easy to lose, so they often show positive trivalence. However, three electrons are obviously more stable than the one electron in the outermost shell of sodium and the two electrons in the outermost shell of magnesium, so Aluminum is less reactive than sodium and magnesium.
Why is aluminum said to be a flying metal?
The density of aluminum is small, only 2.7g/cm³. There is a dense Al₂O₃ film on the surface, which prevents the internal aluminum from reacting and is not easily oxidized. It is a commonly used material in aircraft. 70% of modern aircraft are made of aluminum and aluminum alloys, so it is called flying metal.
Aluminum packaging materials for all-aluminum cans are a symbol of a country's aluminum processing level.
