Why does radon's configuration include 4f¹⁴?

The 4f subshell fills during the lanthanide series (elements 57–71, cerium through lutetium). By the time electrons reach radon (Z=86), the 4f subshell has long been filled with its maximum 14 electrons. These 4f electrons are part of the core and are counted inside the [Xe] notation only in abbreviated form — the full notation writes them explicitly.

How many valence electrons does radon have?

Radon has 8 valence electrons (2 in 6s and 6 in 6p), completing the octet in Period 6. The inner 4f and 5d subshells are core, not valence, in standard chemistry.

Is radon chemically reactive?

Radon is chemically inert under ordinary conditions, just like other noble gases. However, its radioactivity (half-life of Rn-222 ≈ 3.82 days) makes it hazardous in enclosed spaces. Theoretical predictions and some experimental evidence suggest radon could form compounds (e.g., RnF₂) given its large, polarizable electron cloud and low ionization energy (1037 kJ/mol), even lower than xenon's.

What block and period is radon in?

Radon is in Period 6, Group 18 (noble gases), and belongs to the p-block of the periodic table. It sits between astatine (Z=85) and francium (Z=87).

Why is radon radioactive when other noble gases are not?

Radon has no stable isotopes. All isotopes of radon undergo radioactive decay — typically alpha or beta emission. Rn-222 (the most abundant naturally occurring isotope) is produced by the alpha decay of radium-226 in uranium and thorium decay chains. Its instability is nuclear, not electronic: the electron configuration is a closed shell like other noble gases, but the nucleus has an unfavorable proton-to-neutron ratio.

What comes after radon in the periodic table?

After radon (Z=86) comes francium (Z=87) with configuration [Rn] 7s¹, and then radium (Z=88) with [Rn] 7s². Radon's filled configuration defines the [Rn] noble-gas core used for the actinide series and all Period 7 elements.

Radon Electron Configuration

Name: Radon Electron Configuration
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Author: Nham Vu

Reference for radon's electron configuration (1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d¹⁰ 6s² 6p⁶ or [Xe] 4f¹⁴ 5d¹⁰ 6s² 6p⁶), orbital box diagram, quantum numbers, and its position as the heaviest naturally occurring noble gas.

Z = 86 Rn Radon

Radon — Electron Configuration

Atomic number 86 · Radioactive noble gas · Period 6, Group 18 · p-block

[Xe] 4f¹⁴ 5d¹⁰ 6s² 6p⁶ 86 electrons 8 valence e⁻ Defines [Rn] core

Subshell Breakdown

Subshell	Type	Electrons	Max 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 (lanthanide)	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 (valence)	6	6	6p⁶
Total		86

Full Configuration

1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d¹⁰ 6s² 6p⁶

All 15 subshells written explicitly.

Noble-Gas Shorthand

[Xe] 4f¹⁴ 5d¹⁰ 6s² 6p⁶

[Xe] = 1s² … 5p⁶ (xenon's filled 54-electron core).

Defines Core ([Rn])

[Rn] = 1s²…6p⁶

Shorthand for francium, radium, and all actinide elements.

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 18 / 50 electrons (36%)

Shell 6 (n=6) — 6s² 6p⁶ 8 / 72 electrons (11%)

Shell 4 can hold up to 32 electrons (4s + 4p + 4d + 4f) — radon fills all 32 via the lanthanide 4f block. Shell 5 can hold 50 electrons but radon fills only 18 (5s + 5p + 5d), leaving 5f empty. Shell 6 fills only 8 (6s + 6p); the remaining 6d, 6f, and 7s+ are empty and belong to the actinide and later series.

Elements That Use [Rn] as Their Core

Element	Z	Configuration
Francium (Fr)	87	[Rn] 7s¹
Radium (Ra)	88	[Rn] 7s²
Actinium (Ac)	89	[Rn] 6d¹ 7s²
Thorium (Th)	90	[Rn] 6d² 7s²
Uranium (U)	92	[Rn] 5f³ 6d¹ 7s²
Plutonium (Pu)	94	[Rn] 5f⁶ 7s²
Oganesson (Og)	118	[Rn] 5f¹⁴ 6d¹⁰ 7s² 7p⁶

Orbital Box Diagram

Each box represents one orbital. Up arrow = spin +½, down arrow = spin −½. All radon orbitals are fully paired (diamagnetic).

2 e⁻ — filled

6 e⁻ — filled

2 e⁻ — filled

6 e⁻ — filled

10 e⁻ — filled

2 e⁻ — filled

6 e⁻ — filled

10 e⁻ — filled

14 e⁻ — filled

2 e⁻ — filled

6 e⁻ — filled

10 e⁻ — filled

2 e⁻ — filled (valence)

6 e⁻ — filled (valence)

Every orbital in radon holds two electrons with opposite spins (+½ and −½). There are no unpaired electrons — radon is diamagnetic. The highlighted 6s and 6p subshells are the valence orbitals. The 4f row (7 orbitals, 14 electrons) reflects the complete lanthanide filling.

Quantum Numbers — Valence Shell (6s² 6p⁶)

e⁻ #	n	l	mₗ	mₛ	Subshell
79	6	0	0	+½	6s
80	6	0	0	−½	6s
81	6	1	-1	+½	6p
82	6	1	-1	−½	6p
83	6	1	0	+½	6p
84	6	1	0	−½	6p
85	6	1	1	+½	6p
86	6	1	1	−½	6p

n = principal quantum number; l = azimuthal (l=0 → s, l=1 → p); mₗ = magnetic; mₛ = spin. Electrons 1–78 fill the inner core subshells (1s through 5d) with analogous quantum numbers.

Summary

How it works

The Aufbau principle fills subshells from lowest to highest energy: 1s → 2s → 2p → 3s → 3p → 4s → 3d → 4p → 5s → 4d → 5p → 6s → 4f → 5d → 6p.
Radon's 86 electrons completely fill sixteen subshells across six principal shells.
The 4f subshell (14 electrons across seven orbitals) is filled as part of the lanthanide series before 5d and 6p are completed.
The filled 6p subshell (6 electrons across three orbitals) is the outermost and closes radon's valence shell.
With no unpaired electrons and a complete outer shell, radon has zero chemical valence under ordinary conditions.
In noble-gas notation, [Xe] replaces the first 54 electrons; the remaining 32 electrons are written explicitly as 4f¹⁴ 5d¹⁰ 6s² 6p⁶.
Use the tabs below to explore the configuration table, orbital diagram, and element properties.

Use cases

Quick reference for chemistry homework or exams on noble-gas and Period 6 configurations.
Understand why radon is the heaviest naturally occurring noble gas and why it is radioactive.
Use [Xe] shorthand correctly when writing configurations for elements Z=55 through Z=86.
Visualize the fully paired 6p subshell that closes Period 6 of the periodic table.
Compare radon to xenon ([Xe]), krypton ([Kr]), and other noble-gas cores.
Teaching aid for Aufbau principle, Hund's rule, and Pauli exclusion principle with a Period 6 element.
Reference quantum numbers for radon's valence electrons in advanced chemistry and radiochemistry courses.
Understand the role of radon in indoor air quality and radiation safety contexts.

Frequently Asked Questions

Last updated: 2026-07-23 · Reviewed by Nham Vu

Radon Electron Configuration

Radon — Electron Configuration

Subshell Breakdown

Shell Fill Summary

Elements That Use [Rn] as Their Core

Orbital Box Diagram

Quantum Numbers — Valence Shell (6s² 6p⁶)

Identity

Physical Properties

Electronic Properties

Context & Uses

Summary

How it works

Use cases

Frequently Asked Questions

What is the electron configuration of radon?

Why does radon's configuration include 4f¹⁴?

How many valence electrons does radon have?

Is radon chemically reactive?

What block and period is radon in?

Why is radon radioactive when other noble gases are not?

What comes after radon in the periodic table?