Lanthanum

Lanthanum opens the lanthanide series, 15 metallic elements with very similar chemistry that fill the f-block of the periodic table. It is used in camera lenses, hybrid car batteries and as a catalyst in refining crude oil into petrol.

• Atomic Number5757 protons, 57 electrons
• Atomic Mass138.9055 u57× heavier than hydrogen
• State at Room TempSolidSolid
• Density6.15 g/cm³
• Melting / Boiling917.9°C / 3463.8°C
• Discovered1839

What is Lanthanum?

Lanthanum is a soft, silvery-white rare earth metal and the first of the lanthanide series. It readily gives away three electrons to form La³⁺ ions. Because its 4f electron subshell is empty, lanthanum's chemistry is less complex than other lanthanides.

Lanthanum is named from the Greek lanthano meaning to lie hidden, it was hidden as an impurity in cerium oxide for years before being recognised as a distinct element. Carl Gustaf Mosander discovered it in 1839.

Fact Lanthanum compounds were used to create the La₂Zr₂O₇ thermal barrier coating on jet turbine blades, allowing engines to run hotter and more efficiently than any previous material could withstand.

Where you find Lanthanum

On Earth

Rare earth deposits in China, Russia, India and Australia. China produces over 60% of world supply.

How we use Lanthanum

• Lanthanum oxide gives glass lenses an unusually high refractive index, enabling more compact, high-quality camera and telescope lenses.. Camera lenses
• Lanthanum nickel hydride is the hydrogen-absorbing material in nickel-metal hydride (NiMH) batteries, used in hybrid vehicles.. Hybrid car batteries
• Lanthanum oxide catalysts are used in fluid catalytic cracking (FCC), the main process for refining crude oil into petrol and jet fuel.. Oil refining

How it was discovered

Lanthanum is named from the Greek lanthano meaning to lie hidden, it was hidden as an impurity in cerium oxide for years before being recognised as a distinct element. Carl Gustaf Mosander discovered it in 1839.

Deeper dive: lanthanum and the lanthanide series

The lanthanides (elements 57-71) are characterised by the progressive filling of the 4f electron subshell. Because the 4f electrons are deep inside the atom and shielded by outer electrons, they have little effect on chemical bonding. All lanthanides have very similar chemical behaviour, forming +3 ions of comparable size. This similarity makes them extraordinarily difficult to separate from each other, historically requiring hundreds of fractional crystallisation steps. Ion exchange chromatography and solvent extraction methods, developed in the 1940s, finally made pure lanthanides available in quantity.

The term "rare earth" is historically misleading. Most lanthanides are as abundant as copper or nickel in the Earth's crust. The challenge is not scarcity but concentration: they are geochemically dispersed and rarely form rich mineral deposits. The name stuck from the 18th century when they were genuinely difficult to isolate.

Moving to 58 protons brings us to the next element in this remarkable family.