Which is the most abundant metal in the Earth's crust?

Aluminium is the most abundant metal in the Earth's crust, making up about 8 per cent of the crust by weight. It is the third most abundant element in the crust, after oxygen and silicon.

Most abundant elements in the Earth's crust (by weight, approximately):

• Oxygen: about 46 per cent.
• Silicon: about 28 per cent.
• Aluminium: about 8 per cent.
• Iron: about 5 per cent.
• Calcium: about 3.6 per cent.
• Sodium: about 2.8 per cent.
• Potassium: about 2.6 per cent.
• Magnesium: about 2.1 per cent.
• These eight elements together make up nearly 99 per cent of the Earth's crust.

Why aluminium is not found as a free metal:

Aluminium is very reactive, so it never occurs naturally in pure form. It is always combined with other elements, mainly in silicate minerals and clays.

Its main commercial ore is bauxite, a rock rich in hydrated aluminium oxides.

Although aluminium is very abundant, it was once more expensive than gold, because it was so difficult to extract.

The Hall-Heroult electrolytic process (1886) made aluminium cheap enough for everyday use.

Properties and uses of aluminium:

• It is light (about one-third the weight of steel), strong when alloyed, a good conductor of heat and electricity, and resistant to corrosion because it forms a thin protective oxide layer.
• It is used in aircraft, vehicles, power lines, packaging (cans and foil), window frames, utensils and construction.

Other "most abundant" facts:

• Oxygen is the most abundant element in the Earth's crust.
• Iron is the most abundant element in the Earth as a whole, because the core is mostly iron.
• Nitrogen is the most abundant gas in the atmosphere.
• Hydrogen is the most abundant element in the universe.

Why not the other options?

• ✗Iron is the second most abundant metal in the crust.
• ✗Calcium is the third most abundant metal.
• ✗Sodium is the fourth most abundant metal.