Why does ytterbium have a notable +2 oxidation state?

Ytterbium has the ground-state configuration [Xe] 4f¹⁴ 6s². Losing only the two 6s electrons gives Yb²⁺ with configuration [Xe] 4f¹⁴ — a completely filled f subshell. This closed-shell arrangement is especially stable (analogous to Xe core), providing a genuine thermodynamic driving force to stop at +2 rather than proceeding to +3. Yb is one of only three lanthanides (Eu, Sm, Yb) with well-developed divalent chemistry under ordinary conditions.

Why is +3 still the dominant state if +2 is so stable?

The +3 state remains dominant because the third ionization energy (removing one 4f electron from Yb²⁺) is still low enough that most reagents and lattice energies favor the trivalent state. The Yb³⁺ ion is the thermodynamic product in aqueous solution and in most solid-state oxide/halide chemistry. Yb²⁺ is stable primarily in low-oxidation-state environments, with strongly reducing conditions or in solid compounds such as YbI₂ and YbS.

What compounds contain Yb in the +2 state?

YbI₂ (ytterbium diiodide) is the most accessible Yb²⁺ compound and is used as a single-electron reductant in organic synthesis. YbS and YbSe are semiconducting Yb²⁺ chalcogenides with NaCl crystal structure. YbO exists but is unstable. These divalent compounds are kinetically accessible because iodide and sulfide lattice energies are not large enough to force oxidation to +3.

How is Yb(OTf)₃ used as a Lewis acid catalyst?

Ytterbium(III) triflate, Yb(OTf)₃, is a water-tolerant Lewis acid catalyst widely used in organic synthesis for Diels-Alder reactions, aldol reactions, allylation, and Mannich-type reactions. Unlike many traditional Lewis acids (AlCl₃, BF₃), Yb(OTf)₃ is stable and active in aqueous media and can be recovered and recycled. The high charge density of Yb³⁺ activates carbonyl groups toward nucleophilic attack.

What is the electron configuration of Yb³⁺?

Yb³⁺ has the configuration [Xe] 4f¹³ — one electron short of a completely filled f subshell. It has one unpaired f-electron and is therefore weakly paramagnetic. This contrasts with Yb²⁺ ([Xe] 4f¹⁴), which is diamagnetic (all electrons paired). The difference is detectable by magnetic susceptibility measurements and is used to distinguish the two oxidation states experimentally.

How does ytterbium relate to yttrium?

Both Yb and Y were discovered from mineral ores near Ytterby, Sweden (along with Er and Tb — all four named after the same village). Ytterbium (Z=70) is a heavy lanthanide; yttrium (Z=39) is a d-block element in period 5 that behaves chemically like a lanthanide due to similar ionic radius. Yb³⁺ (86.8 pm, 6-coord) and Y³⁺ (90.0 pm) are close enough in size that they frequently co-occur in minerals and are difficult to separate.

Ytterbium Oxidation States Reference

Name: Ytterbium Oxidation States Reference
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Author: Nham Vu

Reference for ytterbium oxidation states: dominant +3, notable +2 (full 4f¹⁴ shell), electron configuration [Xe] 4f¹⁴ 6s², and key compounds including YbI₂ and Yb₂O₃.

Atomic # 70 Yb Ytterbium

Atomic Mass

173.045 u

Group

Lanthanide

Period

Block

f-block

Electronegativity

1.1 (Pauling)

Oxidation States

+3 (dominant), +2

Ytterbium is an f-block lanthanide with ground-state configuration [Xe] 4f¹⁴ 6s². The dominant state is +3 (losing two 6s and one 4f electron), but Yb is one of the few lanthanides with a well-developed +2 chemistry: Yb²⁺ retains a completely filled 4f¹⁴ shell — a closed-shell configuration that provides genuine thermodynamic stabilization. This makes Yb, along with Eu and Sm, an exceptional case among lanthanides.

State	Name	f-electrons	Config (after Xe)	Stability	Notes
0	Elemental	14	[Xe] 4f¹⁴ 6s²	Elemental metal	Silvery-white, soft metal; full 4f¹⁴ in neutral atom
+2	Ytterbium(II)	14	[Xe] 4f¹⁴	Notable / accessible	Closed-shell 4f¹⁴; diamagnetic; accessible in YbI₂, YbS, YbSe; single-electron reductant
+3	Ytterbium(III)	13	[Xe] 4f¹³	Dominant / stable	One unpaired f-electron; weakly paramagnetic; dominates aqueous and most solid-state chemistry
+4	Ytterbium(IV)	12	[Xe] 4f¹²	Not observed	Would remove a second 4f electron — far too high in energy; purely theoretical

Why Yb²⁺ is accessible
Yb²⁺ has a completely filled 4f¹⁴ shell — every f orbital doubly occupied. This closed-shell arrangement lowers the effective nuclear charge felt by the outermost electrons and is particularly stable, analogous to noble-gas configurations. The third ionization energy of Yb (removing a 4f electron from Yb²⁺) is high enough that reducing environments or soft-lattice compounds (iodides, sulfides) can stabilize +2.

Yb³⁺ vs. Yb²⁺ magnetism
Yb³⁺ is weakly paramagnetic: its [Xe] 4f¹³ configuration has one unpaired electron (one hole in the filled shell). Yb²⁺ is diamagnetic: the 4f¹⁴ shell is fully paired. Magnetic susceptibility measurements cleanly distinguish the two states. Yb³⁺ also has a non-zero J ground state (J = 7/2) giving a small but measurable effective magnetic moment (≈4.54 BM).

Most ytterbium compounds contain Yb³⁺, but Yb is exceptional among lanthanides in having a significant body of Yb²⁺ chemistry. The table below covers both oxidation states, including synthetic and catalytic applications.

Compound	Formula	Yb State	Appearance	Notes
Ytterbium(III) Oxide	Yb₂O₃	+3	White cubic solid	Most common Yb oxide; cubic bixbyite structure; used in optical coatings, laser host materials, and as a precursor for other Yb compounds.
Ytterbium(III) Chloride	YbCl₃	+3	White hygroscopic solid	Common laboratory reagent; soluble in water and polar solvents; used in synthesis of organometallic Yb compounds.
Ytterbium(III) Fluoride	YbF₃	+3	White solid	Very low solubility; used in optical fiber amplifiers (Yb-doped fiber) and fluoride glass compositions.
Ytterbium(III) Triflate	Yb(OTf)₃	+3	White powder	Water-tolerant Lewis acid catalyst; effective for Diels-Alder, aldol, allylation, and Mannich reactions in aqueous media; recoverable and reusable.
Ytterbium(III) Nitrate	Yb(NO₃)₃	+3	Colorless crystals	Highly soluble; used in solution-phase synthesis and as an aqueous Yb source for precipitation and sol-gel processes.
Ytterbium(II) Iodide	YbI₂	+2	Dark green solid	Accessible Yb²⁺ compound; single-electron reductant used in organic synthesis (radical cyclizations, ketone/aldehyde reductions) analogous to SmI₂.
Ytterbium(II) Sulfide	YbS	+2	Dark solid	NaCl crystal structure; narrow-gap semiconductor; metallic conductivity near room temperature due to Yb valence fluctuation.
Ytterbium(II) Selenide	YbSe	+2	Dark solid	NaCl structure; divalent Yb chalcogenide; studied for mixed-valence and heavy-fermion behavior.
Ytterbium Aluminate	YbAlO₃	+3	Colorless crystal	Perovskite-type structure; phosphor host material when doped with activators; studied for laser applications.

YbI₂ as a reductant
Ytterbium(II) iodide (YbI₂) is used in organic synthesis as a mild single-electron reductant, similar to the more common samarium(II) iodide (SmI₂). It reduces ketones, aldehydes, and imines, and mediates radical cyclizations and reductive coupling reactions. The Yb²⁺/Yb³⁺ couple (E° ≈ −1.15 V vs. SHE) is less reducing than Sm²⁺/Sm³⁺ (−1.33 V), making YbI₂ selective for certain substrates that would over-reduce with SmI₂.

Yb (neutral)

4f orbitals

↑ ↓

14 f-electrons — all paired (diamagnetic)

Full config: [Xe] 4f¹⁴ 6s²

All 14 f-orbitals fully occupied; 2 s-electrons in outer shell. Diamagnetic atom. The 4f¹⁴ shell is completely filled even before ionization — this is why Yb²⁺ is so accessible (just remove the 6s² pair).

Yb³⁺

4f orbitals

↑ ↓

13 f-electrons — 1 unpaired (weakly paramagnetic)

Full config: [Xe] 4f¹³

Loses 6s² and one 4f electron. Leaves one hole in 4f¹⁴ — one unpaired electron. Weakly paramagnetic; ground state J = 7/2 (²F₇/₂); effective magnetic moment ≈ 4.54 BM.

Why Yb is different from most lanthanides
Most lanthanides (Ce through Lu, excluding Eu and Yb) have 4fⁿ 6s² configurations where removing three electrons (6s² + one 4f) to reach +3 does not create a specially stable electronic arrangement. Ytterbium is an endpoint exception: its neutral atom already has a fully filled 4f¹⁴, so Yb²⁺ ([Xe] 4f¹⁴) retains that closed shell. This parallels how europium (Eu, [Xe] 4f⁷ 6s²) gains a half-filled 4f⁷ in the +2 state — both are energetically special configurations.

Ionization	Energy (kJ/mol)	Electron removed from
IE₁ → Yb⁺	603	6s (outermost electron in neutral Yb)
IE₂ → Yb²⁺	1174	6s (removes second 6s electron; leaves 4f¹⁴)
IE₃ → Yb³⁺	2417	4f (removes one 4f electron from closed shell — large jump)
IE₄ → Yb⁴⁺	4204	4f (another f electron; not chemically accessible)

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Summary

Reference for ytterbium oxidation states: dominant +3, notable +2 (full 4f¹⁴ shell), electron configuration [Xe] 4f¹⁴ 6s², and key compounds including YbI₂ and Yb₂O₃.

How it works

Click a tab — Oxidation States, Compounds, Electron Config, or Physical Props — to explore each section.
The Oxidation States panel lists all known states with stability, f-electron count, and key notes.
The Compounds panel shows common ytterbium compounds, including the notable Yb(II) divalent series.
The Electron Config panel shows orbital diagrams for Yb and Yb³⁺ side by side with ionization energies.
The Physical Props panel provides atomic and material data for quick reference.
Click any monospace table cell to copy its value to the clipboard.

Use cases

Students learning f-block (lanthanide) chemistry and why Yb has unusually stable +2 chemistry.
Chemistry teachers explaining the role of filled 4f¹⁴ shells in stabilizing divalent lanthanides.
Researchers exploring Yb(OTf)₃ as a water-tolerant Lewis acid catalyst in organic synthesis.
Anyone studying inorganic or coordination chemistry covering lanthanide oxidation state trends.
Exam revision for f-block periodic trends, electron configurations, and lanthanide contraction.

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Last updated: 2026-07-24 · Reviewed by Nham Vu