What is the atomic number of Lanthanum?

Lanthanum has atomic number 57, placing it at the start of the lanthanide series in period 6 of the periodic table.

What is the electron configuration of Lanthanum?

The full configuration is [Xe] 5d¹ 6s², meaning it has one electron in the 5d subshell and two in the 6s subshell beyond the xenon core.

What oxidation state does Lanthanum commonly have?

Lanthanum almost exclusively forms +3 compounds (La³⁺), which is the most stable and common oxidation state for all lanthanides.

Is Lanthanum a rare-earth element?

Yes. Lanthanum is both a rare-earth element and the first member of the lanthanide series (elements 57–71), though it is not particularly rare in Earth's crust (~32 ppm).

What are common uses of Lanthanum?

Lanthanum is used in camera and telescope lenses (as La₂O₃ glass), hydrogen storage alloys (NiMH batteries), fluid catalytic cracking catalysts in oil refining, and as a dopant in special optical materials.

What is the atomic mass of Lanthanum?

The standard atomic weight of Lanthanum is 138.905 u (unified atomic mass units), based on the two stable isotopes ¹³⁸La and ¹³⁹La.

Lanthanum Element Properties

Name: Lanthanum Element Properties
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Author: Nham Vu

Interactive reference card for Lanthanum (La, #57) — explore atomic data, electron configuration, physical constants, and chemical behavior in one place.

57 La 138.905

Lanthanum

Lanthanide series · Period 6 · Group 3 (IUPAC)

Soft, silvery-white rare-earth metal. First member of the lanthanide series. Highly reactive with water and air. Named from the Greek lanthanein ("to lie hidden").

Lanthanide Rare Earth Metal Solid at STP

Symbol

Atomic Number

Atomic Mass

138.905 u

Summary

Interactive reference card for Lanthanum (La, #57) — explore atomic data, electron configuration, physical constants, and chemical behavior in one place.

How it works

The card loads with all known Lanthanum properties pre-filled — no input required.
Click any section tab (Overview, Atomic, Physical, Chemical) to jump to that data group.
Use the Copy button next to any value to copy it to your clipboard instantly.
The electron configuration diagram shows subshell occupancy visually.
All values are sourced from IUPAC 2021 standard atomic weights and NIST data.

Use cases

Quick homework or exam reference for Lanthanum atomic data.
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Students learning electron configuration and periodic trends.
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Science fair projects exploring the lanthanide series.

Frequently Asked Questions

Last updated: 2026-06-18 · Reviewed by Nham Vu