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

Scandium has the electron configuration [Ar] 3d1 4s2. Losing all three outer electrons (2 from 4s and 1 from 3d) gives Sc3+ the stable [Ar] noble-gas configuration. The third ionization energy is not prohibitively high because it removes the lone 3d electron; the large lattice and hydration energies of Sc3+ more than compensate, making +3 strongly favored.

Does scandium ever show +1 or +2 oxidation states?

Rarely. +1 and +2 states have been documented in gas-phase or matrix-isolation experiments and in a handful of organometallic or low-temperature compounds, but they are not encountered in ordinary aqueous or solid-state chemistry. Sc3+ is overwhelmingly dominant.

What is the electron configuration of Sc3+?

Scandium in the +3 state has lost its two 4s electrons and the single 3d electron, leaving [Ar] = 1s2 2s2 2p6 3s2 3p6 — identical to the argon noble-gas configuration. This 18-electron core is especially stable.

Is scandium really a transition metal if it only shows one oxidation state?

By IUPAC strict definition, a transition metal forms at least one stable ion with a partially filled d subshell. Sc3+ has a completely empty d shell ([Ar]), so scandium is sometimes called a "border-line" or "pre-transition" metal, though it sits in Group 3 of the d-block and is routinely grouped with the transition metals in periodic table conventions.

What are the most common scandium compounds?

Scandium(III) oxide (Sc2O3), scandium(III) chloride (ScCl3), and scandium(III) hydroxide (Sc(OH)3) are the most common. All feature Sc in the +3 state. ScCl3 is used as a Lewis-acid catalyst, and Sc2O3 is used in specialty ceramics and solid-oxide fuel cells.

How does scandium compare to other Group 3 elements?

Group 3 includes Sc, Y, La, and Ac. All show +3 as their dominant (and for most purposes exclusive) oxidation state. Scandium is the lightest, smallest, and has the highest charge density of the group, making Sc3+ a stronger Lewis acid than Y3+ or La3+.

Scandium Oxidation States

Name: Scandium Oxidation States
Availability: InStock
Author: Nham Vu

Reference for scandium oxidation states: Sc is almost exclusively +3 in compounds, explained through its d-block position, electron configuration, and representative compounds.

Atomic # 21 Sc Scandium

Atomic Mass

44.9559 u

Group

3 (IIIB)

Period

Block

d-block

Electronegativity

1.36 (Pauling)

Oxidation States

+3 (dominant)

Scandium has one dominant oxidation state: +3. Its ground-state configuration is [Ar] 3d¹ 4s² — losing all three outer electrons gives Sc³⁺ the stable [Ar] noble-gas configuration (18 electrons, empty d shell). As the first d-block element in Period 4, scandium sits right at the boundary between the s- and d-blocks; its single 3d electron is not strongly protected by the core, so loss of all three outer electrons is thermodynamically favorable in virtually every compound. The +1 and +2 states exist only in exotic gas-phase or cryogenic matrix environments.

Oxidation State	Stability	Notes
+3	Stable — universal	Found in all ordinary compounds. Sc loses its 4s² and 3d¹ electrons to reach the stable [Ar] core. Sc³⁺ is a hard, triply-charged cation with high charge density; large lattice and hydration energies drive the reaction thermodynamically.
+2	Rare / exotic	Documented in gas-phase molecules (e.g., ScO⁺ in matrix isolation) and some organometallic systems. Not stable in solution or in ordinary solid compounds.
+1	Rare / exotic	Observed only under highly reducing conditions (low-temperature matrices, certain sandwich complexes). Thermodynamically unstable under ordinary conditions.
0	Elemental only	Assigned to pure scandium metal by convention. Silvery-white, soft metal that tarnishes slowly in air. Not a compound oxidation state.

Ionization Energies
IE₁ = 633.1 kJ/mol | IE₂ = 1235 kJ/mol | IE₃ = 2389 kJ/mol | IE₄ = 7089 kJ/mol
The large jump from IE₃ to IE₄ (2389 vs 7089 kJ/mol) confirms +3 as the practical ceiling — the fourth ionization would break into the stable [Ar] noble-gas core.

All stable scandium compounds feature Sc in the +3 oxidation state. Sc³⁺ is a hard Lewis acid with a high charge-to-radius ratio (ionic radius ~0.745 Å for 6-coordinate), making it a strong electrophile and a useful catalyst in organic synthesis.

Compound	Formula	Sc State	Notes
Scandium(III) Oxide	Sc₂O₃	+3	White solid; used in solid-oxide fuel cells, specialty ceramics, and as a stabilizer in zirconia. The most commercially important Sc compound.
Scandium(III) Chloride	ScCl₃	+3	Anhydrous white solid; a strong Lewis-acid catalyst used in Friedel-Crafts type reactions and asymmetric synthesis. Moisture-sensitive.
Scandium(III) Hydroxide	Sc(OH)₃	+3	White amphoteric hydroxide; precipitates from Sc3+ solutions on addition of base. Dissolves in both strong acids and strong bases.
Scandium(III) Fluoride	ScF₃	+3	Ionic fluoride; negative thermal expansion material — its volume contracts on heating, useful in composite materials.
Scandium(III) Bromide	ScBr₃	+3	Used in metal-halide lamps; small additions of ScBr3 improve color rendering and efficiency of mercury lamps.
Scandium(III) Nitrate	Sc(NO₃)₃	+3	Water-soluble salt used in research; commonly encountered as the hexahydrate. All NO3- anions are in the -1 state, Sc is +3.
Scandium(III) Sulfate	Sc₂(SO₄)₃	+3	Soluble salt; used as a source of Sc3+ in research and electroplating. Sulfate anions are SO4 2- (S is +6).
Scandium(III) Triflate	Sc(OTf)₃	+3	Highly active water-tolerant Lewis-acid catalyst; widely used in organic synthesis including Diels-Alder and aldol reactions.

Ground State Configuration

Core

Core (completes [Ar])

Valence d — lost on ionization to Sc³⁺

Valence s — lost on ionization to Sc³⁺

Notation

Full: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹ 4s²

Noble gas: [Ar] 3d¹ 4s²

Sc³⁺ ion: [Ar] = 1s² 2s² 2p⁶ 3s² 3p⁶

Ionization Steps

[Ar] 3d¹ 4s²

Neutral atom — 3 outer electrons

Sc⁺

[Ar] 3d¹ 4s¹

Remove one 4s electron (IE₁ 633.1 kJ/mol)

Sc²⁺

[Ar] 3d¹

Remove second 4s electron (IE₂ 1235 kJ/mol)

Sc³⁺

[Ar]

Remove 3d¹ electron (IE₃ 2389 kJ/mol) — stable noble-gas core

Sc⁴⁺

[Ne] 3s² 3p⁵

Break into [Ar] core (IE₄ 7089 kJ/mol) — not accessible in ordinary chemistry

Why the large jump at IE₄? The first three ionizations remove the two 4s electrons and the single 3d electron, each step requiring progressively more energy. The fourth ionization (7089 kJ/mol) would pull from the filled 3p shell of the stable [Ar] core — nearly three times the cost of IE₃. This discontinuity directly explains why +3 is the ceiling for scandium in all ordinary chemistry.

Enter a scandium compound formula below. The calculator identifies the anion (or overall charge) and uses charge balance to determine the oxidation state of Sc. Supports common anions: O^2-, Cl^-, F^-, Br^-, I^-, OH^-, NO₃^-, SO₄^2-, CO₃^2-, PO₄^3-.

Compound Formula

Quick examples: , , , ,

Charge Balance Reference

Anion	Charge	Example Compound	Sc State
O²⁻	−2	Sc₂O₃	+3
Cl⁻	−1	ScCl₃	+3
F⁻	−1	ScF₃	+3
Br⁻	−1	ScBr₃	+3
OH⁻	−1	Sc(OH)₃	+3
NO₃⁻	−1	Sc(NO₃)₃	+3
SO₄²⁻	−2	Sc₂(SO₄)₃	+3
PO₄³⁻	−3	ScPO₄	+3

Copied!

Summary

Reference for scandium oxidation states: Sc is almost exclusively +3 in compounds, explained through its d-block position, electron configuration, and representative compounds.

How it works

Click a tab — Oxidation States, Compounds, Electron Config, or Formula Calculator — to explore each area.
The Oxidation States panel explains why +3 dominates, covering the +1, +2, and rare 0 states as well.
The Compounds panel lists key scandium compounds with formulas and oxidation state assignments.
The Electron Config panel shows the orbital diagram and explains how losing three electrons gives Sc3+ the stable [Ar] noble-gas configuration.
The Formula Calculator panel lets you enter a compound formula and identify the oxidation state of Sc based on charge balance rules.
Click any monospace table cell to copy its value to your clipboard.

Use cases

Students studying d-block (transition metal) chemistry and oxidation state rules.
Chemistry teachers preparing lessons on Period 4 elements and first-row transition metals.
Researchers needing quick atomic or compound data for scandium.
Anyone studying coordination chemistry, ceramics, or scandium-based alloys.
Students preparing for chemistry exams covering Group 3 or d-block elements.

Frequently Asked Questions

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