What is the electron configuration of cerium?

Cerium (Ce, Z=58) has the ground-state configuration 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 4f¹ 5d¹ 6s². In noble-gas shorthand this is [Xe] 4f¹ 5d¹ 6s², with 58 total electrons.

Why is cerium's electron configuration anomalous?

Standard Aufbau filling would predict [Xe] 4f² 6s² (two electrons in 4f, none in 5d). Instead, cerium adopts [Xe] 4f¹ 5d¹ 6s² because the 4f and 5d subshells are almost identical in energy at Z=58, and occupying both orbitals lowers electron–electron repulsion slightly. This is one of several f-block exceptions to the Aufbau rule.

How many valence electrons does cerium have?

Cerium has 4 valence electrons: one 4f¹, one 5d¹, and two 6s². Losing three gives Ce³⁺ (the most common ion); losing all four gives Ce⁴⁺ with an empty 4f shell isoelectronic with xenon.

What is the noble-gas shorthand for cerium?

The condensed notation is [Xe] 4f¹ 5d¹ 6s², where [Xe] represents the filled 54-electron xenon core (1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁶).

What oxidation states does cerium form and why?

Cerium forms +3 (Ce³⁺, most stable) and +4 (Ce⁴⁺). Ce³⁺ results from losing the 5d¹ and 6s² electrons plus one 4f electron. Ce⁴⁺ results from losing all four valence electrons, leaving an empty 4f shell — a configuration isoelectronic with Xe, which is unusually stable. The Ce³⁺/Ce⁴⁺ redox couple (E° ≈ +1.72 V) makes Ce(IV) a powerful oxidizing agent in analytical chemistry.

What block and period is cerium in?

Cerium is in Period 6 and is the second member of the lanthanide (f-block) series. Despite having a 5d electron it is classified as an f-block element. Its group number is formally 3 in some conventions, though lanthanides are often listed separately below the main table.

What are the quantum numbers for cerium's 4f valence electron?

The 4f¹ electron has n=4, l=3, mₗ=0 (any of −3 to +3 by convention), mₛ=+½. The 5d¹ electron has n=5, l=2, mₗ=0, mₛ=+½. The two 6s² electrons have n=6, l=0, mₗ=0, with mₛ=+½ and −½ respectively.

Cerium Electron Configuration

Name: Cerium Electron Configuration
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Author: Nham Vu

Interactive reference for cerium's anomalous electron configuration ([Xe] 4f¹ 5d¹ 6s²), orbital box diagram, quantum numbers, and key chemical properties of element 58.

Z = 58 Ce Cerium

Cerium — Electron Configuration

Atomic number 58 · Lanthanide (rare earth) · Period 6, f-block · Anomalous 4f/5d filling

[Xe] 4f¹ 5d¹ 6s² 58 electrons 4 valence e⁻ +3 / +4 states

Aufbau Anomaly

Predicted filling would give [Xe] 4f² 6s², but cerium uses [Xe] 4f¹ 5d¹ 6s². The 4f and 5d subshells are nearly degenerate in energy at Z=58, so occupying both reduces electron repulsion. This dual occupancy enables both +3 and +4 oxidation states.

Subshell Breakdown (valence region shown explicitly)

Subshell	Type	Electrons	Max	Notation
[Xe] core	shells 1–5 (1s through 5p)	54	54	[Xe]
4f	f orbitals, shell n=4	1	14	4f¹
5d	d orbitals, shell n=5	1	10	5d¹
6s	s orbital, shell n=6	2	2	6s²
Total		58

Full Configuration

1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 4f¹ 5d¹ 6s²

All subshells written explicitly. 58 electrons total.

Noble-Gas Shorthand

[Xe] 4f¹ 5d¹ 6s²

[Xe] = 54-electron xenon core (1s² through 5p⁶).

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 4f¹ 19 / 32 electrons (59%)

Shell 5 (n=5) — 5s² 5p⁶ 5d¹ 9 / 50 electrons (18%)

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

Shell 4 can hold 32 electrons (4s + 4p + 4d + 4f). Cerium has 19: the 4f subshell just begins filling.

Orbital Box Diagram (valence subshells)

The [Xe] core (54 electrons) is represented in shorthand. Only valence subshells are shown.

[Xe]

54 electrons — xenon core (fully filled 1s through 5p)

empty

1 electron (unpaired, spin up) — anomalous; only 1 of 7 f orbitals occupied

empty

1 electron (unpaired, spin up) — anomalous; coexists with 4f¹ instead of completing 4f²

2 electrons (paired, ↑↓) — filled

Each box represents one orbital. Opposing arrows represent paired electrons (spin +½ and −½). Upward arrow = spin +½. The simultaneous occupancy of 4f and 5d (instead of 4f²) is the Aufbau anomaly unique to cerium among the lanthanides.

Quantum Numbers — Valence Electrons (beyond [Xe] core)

Electron #	n	l	mₗ	mₛ	Subshell	Note
55	4	3	-3	+½	4f	first 4f electron (anomalous)
56	5	2	-2	+½	5d	first 5d electron (anomalous)
57	6	0	0	+½	6s	6s, spin up
58	6	0	0	−½	6s	6s, spin down (paired)

Electrons 1–54 fill the [Xe] core. n = principal; l = azimuthal (l=0→s, l=2→d, l=3→f); mₗ = magnetic; mₛ = spin. mₗ values shown are by convention.

Summary

Interactive reference for cerium's anomalous electron configuration ([Xe] 4f¹ 5d¹ 6s²), orbital box diagram, quantum numbers, and key chemical properties of element 58.

How it works

The Aufbau principle fills orbitals from lowest to highest energy following the (n + l) rule.
Cerium's 58 electrons fill the xenon core (1s through 5p, 54 electrons) plus four valence electrons.
The four valence electrons occupy 4f¹, 5d¹, and 6s² — with one electron in each of 4f and 5d rather than two in 4f.
This anomaly occurs because the 4f and 5d subshells are nearly degenerate in energy at Z=58.
The noble-gas shorthand [Xe] 4f¹ 5d¹ 6s² replaces the 54-electron xenon core with [Xe] in brackets.
The orbital diagram and quantum-number table let you inspect each valence electron individually.

Use cases

Quick reference for chemistry homework or exam review on lanthanide electron configurations.
Understand the 4f¹ 5d¹ 6s² anomaly and why cerium deviates from simple Aufbau filling.
Learn how the dual 4f/5d occupancy enables the Ce³⁺ and Ce⁴⁺ oxidation states.
Compare cerium (Z=58) to neighboring lanthanum (Z=57) and praseodymium (Z=59).
Teaching aid for f-block chemistry, lanthanide contraction, and periodic trends.
Verify quantum numbers for cerium's valence electrons in bonding or spectroscopy work.
Reference cerium's electron structure when studying catalytic converters or rare-earth chemistry.

Frequently Asked Questions

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