Our Elements
Menu

Lanthanum

Element 57 · Lanthanide

Specimen

Atomic number
57
Atomic mass
138.91
State at room temperature
Solid
Melting point
917.9 °C
Boiling point
3,464 °C
Density
6.15 g/cm³
Discovered
1839

Atomic mass from IUPAC.1 Other physical data from PubChem.2

Can I eat it?

In food and water
Not needed, little harm known. Lanthanum has no known function in the body. Lanthanum carbonate is a medicine that binds phosphate in the gut, and the gut absorbs very little lanthanum. The RSC calls lanthanum moderately toxic. 34

See every element.

The atom

La
ShellElectrons
1 (K) 2
2 (L) 8
3 (M) 18
4 (N) 18
5 (O) 9
6 (P) outermost 2
Total57

Configuration [Xe] 5d¹ 6s²

5d ↑
6s ↑ ↓
A shell diagram: each ring is an electron shell and each dot is one electron. The nucleus holds 57 protons. The outermost shell is shown in red. Electrons do not travel on rings: they fill orbitals, regions where an electron is likely to be found. The boxes are those orbitals for the electrons outside the Xe core, with one arrow per electron.

Related elements

Lanthanides
Ce Cerium Pr Praseodymium Nd Neodymium Pm Promethium Sm Samarium Eu Europium Gd Gadolinium Tb Terbium Dy Dysprosium Ho Holmium Er Erbium Tm Thulium Yb Ytterbium Lu Lutetium

New elements by e-mail

Sources

  1. 1

    IUPAC Commission on Isotopic Abundances and Atomic Weights (CIAAW), 2024. Abridged Standard Atomic Weights 2024 .

    The atomic mass shown for the 84 elements that have a standard atomic weight.

  2. 2

    National Center for Biotechnology Information (PubChem), 2026. Periodic Table of Elements .

    Electron configuration, melting and boiling points, density and discovery year for all 118 elements.

  3. 3

    Damment SJP (Renal Failure), 2011. Pharmacology of the Phosphate Binder, Lanthanum Carbonate .

    • Pharmacology of the Phosphate Binder, Lanthanum Carbonate ... poor GI absorption and extensive protein binding
  4. 4

    Royal Society of Chemistry, 2026. Lanthanum - Element information, properties and uses .

    • Lanthanum has no known biological role. Both the element and its compounds are moderately toxic.
  5. 5

    National Institute of Standards and Technology (NIST), 2026. Atomic Weights and Isotopic Compositions for All Elements .

    Isotopic composition of each element; the most abundant isotope sets the neutron count in the nucleus view.