What is the electron configuration of uranium?

Uranium (U, Z=92) has the ground-state configuration [Rn] 5f³ 6d¹ 7s², or in full: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d¹⁰ 6s² 6p⁶ 5f³ 6d¹ 7s².

Why does uranium have both 5f and 6d electrons?

At Z=92 the 5f and 6d sublevels are very close in energy. Three electrons enter 5f and one enters 6d before the 7s orbital fills. This near-degeneracy disappears in heavier actinides where 5f stabilizes and fills completely.

How many valence electrons does uranium have?

Uranium has 6 valence electrons: three in 5f, one in 6d, and two in 7s (5f³ 6d¹ 7s²). The accessible oxidation states (+3 to +6) reflect different combinations of losing these outer electrons.

What block is uranium in?

Uranium is an f-block element, placed in the actinide series. Its primary differentiating electrons are in the 5f subshell, even though one electron also occupies 6d.

What oxidation states does uranium form?

Uranium forms +3, +4, +5, and +6 oxidation states. The +6 state as the uranyl ion UO₂²⁺ is the most common and stable in aqueous solution. U⁴⁺ is also important in nuclear fuel chemistry.

Is uranium radioactive?

Yes. All isotopes of uranium are radioactive. The most abundant natural isotope is U-238 (half-life 4.47 billion years), followed by U-235 (half-life 703.8 million years), the fissile isotope used in nuclear reactors.

Uranium Electron Configuration

Name: Uranium Electron Configuration
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Author: Nham Vu

Reference for uranium's electron configuration: [Rn] 5f³ 6d¹ 7s² (full: 1s²…6p⁶ 5f³ 6d¹ 7s²). Includes orbital filling table, shell breakdown, and why uranium holds both 5f and 6d electrons.

Z = 92 U Uranium

Uranium — Electron Configuration

Atomic number 92 · Actinide series · Period 7 · f-block

[Rn] 5f³ 6d¹ 7s² 92 electrons 6 valence e⁻ 5f³ 6d¹ 7s²

5f and 6d Coexistence

At Z=92 the 5f and 6d sublevels are nearly degenerate in energy. Three electrons populate 5f and one occupies 6d before the outer 7s² shell fills, yielding the ground state [Rn] 5f³ 6d¹ 7s². This mixed occupancy is characteristic of early actinides (Th–Am) where 5f and 6d are so close in energy that small perturbations can shift which one fills. It directly underpins uranium's rich oxidation-state chemistry (+3 through +6) and its behavior as a nuclear fuel.

Noble-Gas Shorthand

[Rn] 5f³ 6d¹ 7s²

[Rn] = 86-electron radon core.

Full Expanded Configuration

1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d¹⁰ 6s² 6p⁶ 5f³ 6d¹ 7s²

All 92 electrons written by subshell.

Subshell Breakdown

Subshell	Type	Electrons	Capacity	Notation
1s	s orbital, shell n=1	2	2	1s²
2s	s orbital, shell n=2	2	2	2s²
2p	p orbitals, shell n=2	6	6	2p⁶
3s	s orbital, shell n=3	2	2	3s²
3p	p orbitals, shell n=3	6	6	3p⁶
3d	d orbitals, shell n=3	10	10	3d¹⁰
4s	s orbital, shell n=4	2	2	4s²
4p	p orbitals, shell n=4	6	6	4p⁶
4d	d orbitals, shell n=4	10	10	4d¹⁰
4f	f orbitals, shell n=4	14	14	4f¹⁴
5s	s orbital, shell n=5	2	2	5s²
5p	p orbitals, shell n=5	6	6	5p⁶
5d	d orbitals, shell n=5	10	10	5d¹⁰
6s	s orbital, shell n=6	2	2	6s²
6p	p orbitals, shell n=6	6	6	6p⁶
5f	f orbitals, shell n=5	3	14	5f³
6d	d orbitals, shell n=6	1	10	6d¹
7s	s orbital, shell n=7	2	2	7s²
Total		92

Valence subshells (5f, 6d, 7s) are highlighted. All others form the [Rn] core.

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 4f¹⁴ 32 / 32 electrons (100%)

Shell 5 (n=5) — 5s² 5p⁶ 5d¹⁰ 5f³ 21 / 32 electrons (66%)

Shell 6 (n=6) — 6s² 6p⁶ 6d¹ 9 / 32 electrons (28%)

Shell 7 (n=7) — 7s² 2 / 32 electrons (6%)

Quantum Numbers for Valence Electrons

Uranium's six valence electrons (5f³, 6d¹, 7s²) each carry four quantum numbers: principal (n), angular momentum (l), magnetic (m_l), and spin (m_s). By Hund's rule the three 5f electrons each occupy separate orbitals with parallel spins before pairing.

Electron	Subshell	n	l	m_l	m_s
5f electron #1	5f	5	3	-3	+½
5f electron #2	5f	5	3	-2	+½
5f electron #3	5f	5	3	-1	+½
6d electron #1	6d	6	2	-2	+½
7s electron #1	7s	7	0	0	+½
7s electron #2	7s	7	0	0	−½

m_l values shown follow standard convention from −l to +l. Hund's rule maximizes total spin, so all three 5f electrons have m_s = +½ before any pairing.

Quantum Number Rules

n Principal quantum number. Determines the shell (1–7 for U). Higher n = larger orbital, more energy.

l Angular momentum. s=0, p=1, d=2, f=3. Defines subshell shape.

m_l Magnetic quantum number. Ranges from −l to +l. Specifies orbital orientation.

m_s Spin. Either +½ (up ↑) or −½ (down ↓). No two electrons in the same atom share all four identical quantum numbers (Pauli exclusion).

Summary

How it works

Uranium's 92 electrons fill orbitals in order of increasing energy following the Aufbau principle.
Radon ([Rn], Z=86) provides the filled core: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d¹⁰ 6s² 6p⁶.
After the [Rn] core, three electrons enter 5f and one enters 6d before filling 7s² — giving [Rn] 5f³ 6d¹ 7s².
The coexistence of 5f and 6d occupancy reflects the near-degeneracy of those sublevels at Z=92.
Valence electrons are 5f³ 6d¹ 7s², giving uranium common oxidation states of +3 through +6, with +6 (UO₂²⁺) being the most stable in solution.
This configuration underpins uranium's unique chemistry and its use as a fissile material in nuclear reactors.

Use cases

Chemistry reference for students studying actinide or f-block element configurations.
Compare uranium's 5f³ 6d¹ 7s² with neighboring actinides like neptunium and thorium.
Understand how the 5f–6d near-degeneracy produces multiple oxidation states.
Verify quantum numbers and subshell counts for exam preparation.
Teaching aid for nuclear chemistry — linking electron configuration to fission properties.
Research reference for understanding uranium's role in the actinide series.

Frequently Asked Questions

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