Why does lanthanum almost always have a +3 oxidation state?

Lanthanum has the ground-state configuration [Xe] 5d1 6s2. Losing all three valence electrons — one 5d and two 6s — gives it the stable [Xe] xenon noble-gas core. The energy recovered from forming La3+ compounds (lattice and hydration energies) greatly exceeds the cost of the three ionizations, making +3 overwhelmingly favored under all ordinary conditions.

Does lanthanum have a +2 or +4 oxidation state?

Stable +2 or +4 compounds of lanthanum are not known under ordinary conditions. Unlike some later lanthanides (Eu2+, Ce4+), lanthanum lacks the half-filled or fully-filled 4f subshell stabilization that would make other oxidation states competitive. Its empty 4f shell gives no special stability for +2 or +4.

What is lanthanum's electron configuration?

Ground state: [Xe] 5d1 6s2. The 4f subshell is completely empty in neutral La, which distinguishes it from most other lanthanides. When ionized to La3+, the 5d1 and 6s2 electrons are removed, leaving the [Xe] core: 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 5s2 5p6.

Why is lanthanum considered the first lanthanide if it has no 4f electrons?

Lanthanum is placed at the start of the lanthanide series by IUPAC convention because it begins Period 6 in Group 3 and its chemistry closely parallels the 4f elements that follow. Its empty 4f shell makes it the archetype for +3 lanthanide behavior. Some periodic table conventions use lutetium (Lu) as the Group 3 member and list La as the true start of the f-block — the debate is ongoing.

What are the most important lanthanum compounds?

Lanthanum oxide (La2O3), lanthanum chloride (LaCl3), lanthanum fluoride (LaF3), lanthanum carbonate (La2(CO3)3), and lanthanum aluminate (LaAlO3, LAO) are the most significant. Lanthanum nickelate (LaNiO3) and related perovskites are important in solid oxide fuel cells and electrode research. All feature La in the +3 state.

How does lanthanum compare to other lanthanides in oxidation state behavior?

Lanthanum is one of the most exclusively +3 lanthanides. Most lanthanides are also primarily +3, but several show accessible +2 (Sm, Eu, Yb) or +4 (Ce, Pr, Tb) states due to extra stability from half-filled (4f7) or filled (4f14) 4f subshells. Lanthanum, with an empty 4f shell and no such special stability, is almost entirely restricted to +3.

Lanthanum Oxidation States

Name: Lanthanum Oxidation States
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Author: Nham Vu

Reference for lanthanum oxidation states: La is overwhelmingly +3, the gateway lanthanide, with its electron configuration, ionization energies, and common compounds explained.

Atomic # 57 La Lanthanum

Atomic Mass

138.905 u

Group

3 (IIIB)

Period

Block

d/f-block

Electronegativity

1.10 (Pauling)

Oxidation States

+3 (dominant)

Lanthanum exhibits one dominant oxidation state: +3. Its ground-state configuration is [Xe] 5d¹ 6s² — losing one 5d and two 6s electrons attains the stable xenon noble-gas core. Unlike later lanthanides that can access +2 or +4 via their 4f electrons, La has an empty 4f subshell, so no competing stable state is accessible under ordinary conditions. All three lanthanide characteristics — ionic radius, basicity, and coordination chemistry — are set by this exclusive +3 behavior.

Oxidation State	Stability	Notes
+3	Stable	Universal state in all stable compounds. La loses 5d¹ 6s² to reach the [Xe] noble-gas configuration. Thermodynamically driven by high lattice and hydration energies of La³⁺.
0	Elemental only	Assigned to pure lanthanum metal by convention. Silvery-white, malleable rare-earth metal that tarnishes rapidly in air.
+2	Not observed	No stable La²⁺ compounds are known. The empty 4f shell provides no half-filled stabilization that would make +2 accessible (contrast with Eu²⁺ which has 4f⁷).
+4	Not observed	La⁴⁺ is unknown. A filled 4f shell (4f¹⁴) is what stabilizes Ce⁴⁺ — La has no 4f electrons to offer, so +4 is not accessible.

Ionization Energies
IE₁ = 538.1 kJ/mol | IE₂ = 1067 kJ/mol | IE₃ = 1850.3 kJ/mol | IE₄ = 4819 kJ/mol
The large jump from IE₃ to IE₄ confirms +3 as the ceiling — IE₄ would break into the stable [Xe] noble-gas core.

All stable lanthanum compounds feature La in the +3 oxidation state. La³⁺ is large (ionic radius ~103 pm in 6-coordination) and strongly basic, making it an effective catalyst support, phosphor host, and electrolyte component. Its large size means it often adopts high coordination numbers (8–12) in crystal structures.

Compound	Formula	La State	Notes
Lanthanum Oxide (Lanthana)	La₂O₃	+3	High-melting refractory oxide; used as a gate dielectric in CMOS transistors and as a catalyst support. Absorbs CO₂ and H₂O from air, forming La(OH)₃ and La₂(CO₃)₃ on exposure.
Lanthanum Chloride	LaCl₃	+3	Highly water-soluble ionic salt; used in biology to block calcium channels and in NMR shift reagent preparations. A common precursor for other La compounds.
Lanthanum Fluoride	LaF₃	+3	Insoluble fluoride with low refractive index; used in optical coatings and fluoride ion-selective electrodes. Host matrix for upconversion nanoparticles.
Lanthanum Hydroxide	La(OH)₃	+3	Formed by hydrolysis of La salts in basic solution. Less amphoteric than aluminium hydroxide — it is a strong base that does not dissolve in excess NaOH.
Lanthanum Carbonate	La₂(CO₃)₃	+3	Used as a phosphate binder (Fosrenol) in renal dialysis patients to control hyperphosphatemia. Practically insoluble in water.
Lanthanum Aluminate	LaAlO₃	+3	Perovskite-structure oxide (LAO); widely used as a substrate for high-temperature superconductor thin films and in CMOS gate dielectrics.
Lanthanum Nickelate	LaNiO₃	+3	Metallic perovskite; studied as an electrode material in solid oxide fuel cells and as a catalyst for oxygen reduction reactions.
Lanthanum Sulfate	La₂(SO₄)₃	+3	Soluble salt used as a laboratory reagent and in analytical chemistry for precipitating rare-earth elements.
Lanthanum Nitrate	La(NO₃)₃	+3	Highly soluble; used in pyrotechnics, catalyst synthesis, and as a reagent. Oxidising in concentrated form.
Lanthanum Hexaboride	LaB₆	+3	Metallic conductor with very low work function; the standard material for high-brightness electron emitters in SEMs and TEMs.

Ground State Configuration

1s–4d

+42

Core [Kr] 4d10 — inner shells, all filled

Empty in La (no 4f electrons in ground state)

5s 5p

Core — part of [Xe] after ionization

One 5d electron — lost on 3rd ionization

Two 6s electrons — lost on 1st and 2nd ionization

Notation

Full: [Xe] 5d¹ 6s²

Expanded: 1s²…4d¹⁰ 5s² 5p⁶ 5d¹ 6s²

La³⁺ ion: [Xe] = …5s² 5p⁶

Ionization Steps to La³⁺

[Xe] 5d¹ 6s²

Neutral — 3 valence electrons (5d¹ 6s²)

La⁺

[Xe] 5d¹ 6s¹

Remove one 6s electron (IE₁ 538.1 kJ/mol)

La²⁺

[Xe] 5d¹

Remove second 6s electron (IE₂ 1067 kJ/mol)

La³⁺

[Xe]

Remove 5d¹ electron (IE₃ 1850.3 kJ/mol) — stable noble-gas core

La⁴⁺

[Xe] − 5p¹

Break into [Xe] core (IE₄ 4819 kJ/mol) — not accessible ordinarily

Why does La have no 4f electrons? In the ground state, the 5d orbital is slightly lower in energy than 4f for lanthanum. The single electron beyond [Xe] enters 5d¹ rather than 4f¹ — confirmed by spectroscopy and computation. This empty 4f shell is precisely what makes La the gateway into the lanthanide series, whose chemistry is defined by the gradual filling of 4f across Ce to Lu.

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Summary

Reference for lanthanum oxidation states: La is overwhelmingly +3, the gateway lanthanide, with its electron configuration, ionization energies, and common compounds explained.

How it works

Click a tab — Oxidation States, Compounds, Electron Config, or Physical Props — to explore each section.
The Oxidation States panel explains why +3 dominates, with a table of all known states and stability notes.
The Compounds panel lists common lanthanum compounds with formulas, oxidation state assignments, and application notes.
The Electron Config panel shows the orbital filling diagram and the three-step ionization path to La3+.
The Physical Props panel provides atomic and material data for quick reference.
Click any monospace table cell to copy its value to your clipboard.

Use cases

Students studying lanthanide chemistry and the f-block for the first time.
Chemistry teachers explaining why the +3 state dominates across the lanthanide series.
Materials scientists working with lanthanum-doped ceramics, phosphors, or perovskites.
Researchers needing atomic data for La in catalyst or battery electrode design.
Anyone preparing for chemistry exams covering Period 6, Group 3, or lanthanide elements.

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Last updated: 2026-07-08 · Reviewed by Nham Vu