Why does europium have 4f⁷ and not 4f⁶ 5d¹?

The Madelung ordering fills 4f before 5d when their n+l values tie because 4f has the lower principal quantum number. Europium therefore reaches [Xe] 4f⁷ 6s² directly; the half-filled 4f subshell is also especially stable.

What are europium's common oxidation states?

Europium exhibits both +3 (losing the 6s² pair and one 4f electron) and +2 (unusually stable because Eu²⁺ retains the half-filled [Xe] 4f⁷ core). The +3 state dominates in most compounds; the +2 state appears in EuO, EuS, and divalent salts.

How many valence electrons does europium have?

Europium has 9 valence electrons in the outermost shells: 7 in 4f and 2 in 6s. Chemically, it typically exposes 2–3 of these (the 6s pair plus one 4f electron) in bonding.

What block and period is europium in?

Europium is in Period 6 and belongs to the f-block (lanthanide series). It sits in Group 3 of the extended periodic table, between samarium (Z=62) and gadolinium (Z=64).

What is europium used for?

Europium is the primary red and blue phosphor activator in fluorescent lamps, CRT screens, and white LEDs. Eu³⁺ emits red light; Eu²⁺ emits blue. It is also used in euro banknote fluorescent security ink.

What is the noble-gas core for europium?

[Xe] represents the 54-electron xenon core: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁶. The remaining 9 electrons (4f⁷ 6s²) are the valence region.

Europium Electron Configuration

Quick reference for europium's ground-state electron configuration [Xe] 4f⁷ 6s², orbital diagram, quantum numbers, oxidation states, and key element facts.

Z = 63 Eu Europium

Europium — Electron Configuration

Atomic number 63 · Lanthanide (rare earth) · Period 6 · f-block

[Xe] 4f⁷ 6s² 63 electrons 9 valence e⁻ +2 / +3 states

Half-filled stability: Aufbau filling gives europium [Xe] 4f⁷ 6s². Its half-filled 4f⁷ subshell has one electron per orbital and additional exchange-energy stability.

Subshell Breakdown (all 63 electrons)

Subshell	Type	Electrons	Max	Notation
1s	s, n=1	2	2	1s²
2s	s, n=2	2	2	2s²
2p	p, n=2	6	6	2p⁶
3s	s, n=3	2	2	3s²
3p	p, n=3	6	6	3p⁶
3d	d, n=3	10	10	3d¹⁰
4s	s, n=4	2	2	4s²
4p	p, n=4	6	6	4p⁶
4d	d, n=4	10	10	4d¹⁰
4f	f, n=4	7	14	4f⁷
5s	s, n=5	2	2	5s²
5p	p, n=5	6	6	5p⁶
6s	s, n=6	2	2	6s²
Total		63

Noble-Gas Shorthand

[Xe] 4f⁷ 6s²

[Xe] = 54-electron xenon core.

Full Configuration

1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f⁷ 5s² 5p⁶ 6s²

All 63 electrons written explicitly.

Shell Fill Summary

Shell 1 (n=1) — 1s² 2 / 2 electrons (100%)

Shell 2 (n=2) — 2s² 2p⁶ 8 / 8 electrons (100%)

Shell 3 (n=3) — 3s² 3p⁶ 3d¹⁰ 18 / 18 electrons (100%)

Shell 4 (n=4) — 4s² 4p⁶ 4d¹⁰ 4f⁷ 25 / 32 electrons (78%)

Shell 5 (n=5) — 5s² 5p⁶ 8 / 50 electrons (16%)

Shell 6 (n=6) — 6s² 2 / 72 electrons (3%)

Shell 4 holds 25 of its maximum 32 electrons. Shell 6 holds only the two 6s electrons — europium has no 6p, 5d, or 5f electrons.

Orbital Box Diagram — Valence Region

The [Xe] core (54 electrons in filled subshells) is collapsed for clarity. Only the 4f and 6s valence subshells are shown.

−3

−2

−1

7 electrons, one per orbital — half-filled 4f⁷ (all spin up, Hund's rule). No paired electrons in 4f.

2 electrons (paired, +½ and −½) — filled

Each box = one orbital. The mₗ values below the 4f boxes run from −3 to +3 (seven 4f orbitals). All seven carry one spin-up electron, giving europium a magnetic moment of 7 unpaired electrons.

Quantum Numbers — 4f and 6s Valence Electrons

Electron	n	l	mₗ	mₛ	Subshell
55 (6s)	6	0	0	+½	6s
56 (6s)	6	0	0	−½	6s
57 (4f)	4	3	-3	+½	4f
58 (4f)	4	3	-2	+½	4f
59 (4f)	4	3	-1	+½	4f
60 (4f)	4	3	0	+½	4f
61 (4f)	4	3	1	+½	4f
62 (4f)	4	3	2	+½	4f
63 (4f)	4	3	3	+½	4f

n = principal; l = azimuthal (l=3 → f); mₗ = magnetic (−l to +l); mₛ = spin. Electrons 1–54 occupy the [Xe] core (all subshells filled).

Common State (Eu³⁺)

Europium loses two 6s electrons and one 4f electron to form Eu³⁺.

Configuration: [Xe] 4f⁶

4f subshell is now partially filled with 6 electrons.

Standard lanthanide state, found in most compounds
Eu₂O₃, EuCl₃, Eu(NO₃)₃ are common Eu³⁺ compounds
Eu³⁺ is the red phosphor activator in fluorescent lamps

Unusual State (Eu²⁺)

Europium loses only its two 6s electrons to form Eu²⁺.

Configuration: [Xe] 4f⁷

Retains the stable half-filled 4f⁷ configuration — this is why Eu²⁺ is accessible.

Rare among lanthanides — most only show +3
EuO, EuS, EuSO₄ contain Eu²⁺
Eu²⁺ emits blue-green luminescence in phosphors

Ionization Summary

Ion	Electrons lost	Resulting config	Stability driver
Eu²⁺	2 (both 6s)	[Xe] 4f⁷	Half-filled 4f⁷ exchange energy
Eu³⁺	3 (6s² + one 4f)	[Xe] 4f⁶	Lanthanide contraction, +3 preferred in aqueous chemistry

Summary

Quick reference for europium's ground-state electron configuration [Xe] 4f⁷ 6s², orbital diagram, quantum numbers, oxidation states, and key element facts.

How it works

Europium's 63 electrons fill subshells following the Aufbau principle.
After xenon, 6s fills before 4f; the resulting [Xe] 4f⁷ 6s² configuration is Aufbau-consistent and has a stable half-filled 4f subshell.
Noble-gas shorthand replaces the inner xenon core ([Xe] = 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁶) with [Xe] in brackets.
The resulting valence region is 4f⁷ 6s²: seven unpaired 4f electrons plus two paired 6s electrons.
Europium commonly forms +3 ions (losing 6s² and one 4f electron → [Xe] 4f⁶) and less commonly +2 ions (losing 6s² → [Xe] 4f⁷).
The half-filled 4f⁷ configuration of Eu²⁺ is especially stable, explaining europium's notable +2 chemistry among lanthanides.

Use cases

Chemistry homework and exam prep on lanthanide electron configurations.
Understanding europium's half-filled 4f subshell compared with neighboring lanthanides.
Reference for +2 vs +3 oxidation state chemistry of rare-earth elements.
Teaching aid for 4f-block filling and Hund's rule in the f-block.
Comparing europium's configuration to gadolinium (half-filled 4f⁷ 5d¹) and samarium.
Materials science: europium is a red/blue phosphor dopant in LEDs and fluorescent lamps.
Verifying quantum numbers for 4f and 6s valence electrons.

Frequently Asked Questions

Last updated: 2026-09-22 · Reviewed by Nham Vu

Europium Electron Configuration

Europium — Electron Configuration

Subshell Breakdown (all 63 electrons)

Shell Fill Summary

Orbital Box Diagram — Valence Region

Quantum Numbers — 4f and 6s Valence Electrons

Common State (Eu³⁺)

Unusual State (Eu²⁺)

Ionization Summary

Identity

Physical Properties

Electronic Properties

Key Uses

Summary

How it works

Use cases

Frequently Asked Questions

Europium Electron Configuration

Use the Europium Electron Configuration

Europium — Electron Configuration

Subshell Breakdown (all 63 electrons)

Shell Fill Summary

Orbital Box Diagram — Valence Region

Quantum Numbers — 4f and 6s Valence Electrons

Common State (Eu³⁺)

Unusual State (Eu²⁺)

Ionization Summary

Identity

Physical Properties

Electronic Properties

Key Uses

Summary

How it works

Use cases

Frequently Asked Questions