What oxidation states can praseodymium have?

Praseodymium most commonly exists in the +3 state, which is overwhelmingly dominant in solution and in most solid compounds. A +4 state is known in a small number of solid-state oxides (e.g., PrO2 and mixed oxides like Pr6O11) but is not stable in aqueous solution. The +2 state is very rare and only observed under extreme conditions in the solid state.

Why is the +3 state so dominant in praseodymium?

Lanthanide elements tend to lose the two 6s electrons and one 4f electron to reach the +3 state because the resulting [Xe] 4f2 configuration (Pr3+) is relatively stable. The 4f orbitals are well shielded from the crystal field and ligand environment, so there is little energetic incentive to oxidize further. The fourth ionization energy of Pr is high enough that +4 is only accessible in strongly oxidizing, solid-state environments.

What is the electron configuration of Pr and Pr3+?

Neutral praseodymium: [Xe] 4f3 6s2 (or [Xe] 4f2 5d1 6s2 in some sources; the 4f3 6s2 form is most commonly cited for ground state). Pr3+ (the dominant ion): [Xe] 4f2. Pr4+: [Xe] 4f1. Losing the 6s and one 4f electron to give Pr3+ is thermodynamically favorable.

What is PrO2 and why does it show Pr in +4?

PrO2 is praseodymium(IV) oxide — one of the few stable +4 compounds of praseodymium. In PrO2, oxygen is -2 (2 atoms × -2 = -4 per formula unit); for the compound to be neutral, Pr must be +4. The +4 state is stabilized here by the high lattice energy of the fluorite-type oxide structure, not by aqueous chemistry.

How is praseodymium used industrially?

The dominant use is as an alloying element in neodymium-iron-boron (NdFeB) permanent magnets, where Pr partly replaces Nd to improve coercivity and reduce costs. Pr6O11 (a mixed Pr3+/Pr4+ oxide) is the main commercial form of praseodymium oxide and is used as a yellow pigment in ceramics and glasses, as a polishing abite, and as a catalyst support.

What is Pr6O11 and what are the oxidation states of Pr in it?

Pr6O11 is a non-stoichiometric mixed-valence oxide containing both Pr3+ and Pr4+ ions. It can be thought of as 4 formula units of Pr2O3 (Pr3+) combined with 1 formula unit of PrO2 (Pr4+): 4(Pr2O3) + PrO2 is not quite right — the correct average is (4 Pr3+ + 2 Pr4+) with 11 O2-. Average oxidation state of Pr in Pr6O11 = (11×2 - 0) / 6 = +22/6 ≈ +3.67, confirming the mixed-valence character.

Praseodymium Oxidation States

Name: Praseodymium Oxidation States
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Author: Nham Vu

Interactive reference for praseodymium (Pr, element 59) oxidation states (+3 dominant, +4 rare), electron configuration, and example compounds with step-by-step assignments.

Atomic # 59 Pr Praseodymium

Atomic Mass

140.908 u

Group

Lanthanides

Period

Block

f-block

Electronegativity

1.13 (Pauling)

Oxidation States

+3 (dom.), +4

Electron Configuration

Neutral Pr

[Xe] 4f³ 6s²

Pr³⁺ (dominant ion)

[Xe] 4f²

Pr⁴⁺ (rare, solid-state)

[Xe] 4f¹

Praseodymium has two known oxidation states. The +3 state is by far the most common. Click a state card to see its compounds and how to identify it.

Oxidation State +3

The +3 state is the dominant and overwhelmingly stable oxidation state of praseodymium under normal chemical conditions — in solution, in the majority of solid compounds, and in most industrial applications. It is reached by removing the two 6s electrons and one 4f electron from neutral Pr, leaving the [Xe] 4f² configuration for Pr³⁺. The resulting ion is pale green in solution and shows characteristic f-f absorption bands in the visible spectrum. Pr₂O₃ and PrCl₃ are the archetypal +3 compounds.

How to Identify This State

In Pr₂O₃: O = -2 (three atoms per formula unit, total -6 per Pr₂O₃). Formula unit is neutral: 2Pr + 3(-2) = 0 → 2Pr = +6 → Pr = +3. In PrCl₃: Cl = -1 (three atoms, total -3). Neutral compound: Pr + 3(-1) = 0 → Pr = +3. In Pr(NO₃)₃: each NO₃^- is -1; three of them total -3; compound neutral → Pr = +3.

Example Compounds

Formula	Name	Assignment	Notes
Pr₂O₃	Praseodymium(III) Oxide	2Pr + 3(-2) = 0 → Pr = +3	White sesquioxide; converts slowly to Pr₆O₁₁ in air. Starting material for many Pr compounds and ceramic pigments.
PrCl₃	Praseodymium(III) Chloride	3(-1) + Pr = 0 → Pr = +3	Green hygroscopic solid used in organometallic synthesis and as a Lewis acid catalyst. Anhydrous form prepared by ammonium chloride route.
Pr(NO₃)₃	Praseodymium(III) Nitrate	3(-1) + Pr = 0 (using NO₃^-) → Pr = +3	Pale green, highly soluble salt widely used as a precursor in sol-gel and hydrothermal synthesis of Pr-doped materials.
PrF₃	Praseodymium(III) Fluoride	3(-1) + Pr = 0 → Pr = +3	Insoluble, thermally stable compound used in optical fiber applications (ZBLAN glass) and vacuum UV lasers.
Pr₂(SO₄)₃	Praseodymium(III) Sulfate	3(-2) + Pr = 0 (using SO₄^2-, 3 ions total -6) → Pr = +3	Water-soluble salt; used in analytical chemistry and as a source of Pr³⁺ ions for doping experiments.

Common Uses

Neodymium-praseodymium (NdPr) alloys for permanent magnets
Yellow-green pigment in ceramic glazes (Pr-doped zirconia)
Optical fiber amplifiers and lasers (Pr3+:fluoride glass)
Carbon arc electrodes for movie projectors and searchlights
High-strength low-alloy (HSLA) steel and magnesium alloy grain refining

Oxidation State +4

The +4 state is rare and only accessible in the solid state under oxidizing conditions. It requires removal of a second 4f electron, giving Pr⁴⁺ with the [Xe] 4f¹ configuration. This is energetically costly — the fourth ionization energy of Pr is high — so the +4 state is stabilized exclusively by high lattice energies in oxide frameworks (fluorite and related structures). PrO₂ is the only binary +4 compound; the more common commercial product Pr₆O₁₁ is a mixed Pr³⁺/Pr⁴⁺ oxide. In aqueous solution Pr⁴⁺ does not exist — it instantly oxidizes water.

How to Identify This State

In PrO₂: O = -2 (two atoms, total -4). Compound is neutral: Pr + 2(-2) = 0 → Pr = +4. In Pr₆O₁₁: O total = 11 × (-2) = -22; six Pr atoms must balance: 6Pr = +22 → average Pr = +3.67 (mixed +3/+4, four Pr³⁺ + two Pr⁴⁺). The +4 state is confirmed experimentally by X-ray diffraction and XANES spectroscopy.

Example Compounds

Formula	Name	Assignment	Notes
PrO₂	Praseodymium(IV) Oxide	Pr + 2(-2) = 0 → Pr = +4	Black fluorite-structure oxide; only stable +4 binary compound of Pr. Prepared by oxidation of Pr₂O₃ under high O₂ pressure or electrochemically.
Pr₆O₁₁	Praseodymium Mixed Oxide	6Pr + 11(-2) = 0 → avg. Pr ≈ +3.67 (4 Pr³⁺ + 2 Pr⁴⁺)	Most common commercial form of praseodymium oxide; yellow-green powder used in ceramic pigments, polishing, and as a catalyst support.
Ba₂PrO₄	Barium Praseodymium(IV) Oxide	2(+2) + Pr + 4(-2) = 0 → Pr = +4	Ternary oxide stabilizing Pr in +4 via high lattice energy of the perovskite-like structure. Research compound.

Common Uses

Pr6O11 yellow-green pigment for ceramics and zirconia glazes
Catalyst support in automotive exhaust purification (CePrOx mixed oxides)
Reference material for studying 4f1 electronic structure and magnetism
Investigation of mixed-valence phenomena in lanthanide oxide materials

Oxidation State Summary

State	Frequency	Key Example	Notes
+3	Dominant	Pr₂O₃, PrCl₃	Formed by losing 2 × 6s + 1 × 4f electrons. Stable in solution and most solids. Pale green Pr3+ ion.
+4	Rare (solid)	PrO₂, Pr₆O₁₁	Only in strongly oxidizing solid-state oxide lattices. Pr4+ is [Xe] 4f1. Not accessible in aqueous solution.

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Summary

Interactive reference for praseodymium (Pr, element 59) oxidation states (+3 dominant, +4 rare), electron configuration, and example compounds with step-by-step assignments.

How it works

Click an oxidation state card (+3 or +4) to open its detail panel.
The detail panel shows a description, example compounds, step-by-step assignment, and identification tips.
Use the Compound Lookup tab to select a known praseodymium compound and see the oxidation state of Pr explained step by step.
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Switch between the Explorer and Compound Lookup tabs using the tab bar at the top.

Use cases

Chemistry students revising lanthanide oxidation state rules and f-block periodicity.
Materials scientists identifying the oxidation state of Pr in ceramic glazes or oxide catalysts.
Teachers preparing reference content on rare-earth element chemistry.
Researchers checking the Pr oxidation state in a specific reagent or alloy precursor.
Engineers selecting praseodymium compounds for permanent magnet or phosphor applications.

Frequently Asked Questions

Last updated: 2026-07-22 · Reviewed by Nham Vu