What is the noble-gas shorthand for radium?

The condensed (noble-gas) notation is [Rn] 7s², where [Rn] stands for the filled radon core — 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d¹⁰ 6s² 6p⁶ — containing 86 electrons.

Why does radium form a +2 ion?

Radium loses its two 7s valence electrons to reach the stable [Rn] noble-gas core (86 electrons), forming Ra²⁺. The +2 state is the only oxidation state observed for radium.

How many valence electrons does radium have?

Radium has 2 valence electrons, both in the 7s subshell. This is characteristic of all Group 2 alkaline earth metals.

What block and period is radium in?

Radium is in Period 7, Group 2 (IIA), and belongs to the s-block of the periodic table. It is the heaviest alkaline earth metal, directly below barium in Group 2.

Is radium radioactive?

Yes. All isotopes of radium are radioactive. The most stable is Ra-226 (half-life ~1,600 years), a decay product of uranium-238. Ra-226 emits alpha particles and decays to radon-222.

What are the quantum numbers for radium's outermost electrons?

The two 7s electrons have: n=7, l=0, mₗ=0, and mₛ=+½ for the first and mₛ=−½ for the second. Both occupy the single 7s orbital with opposite spins.

Radium Electron Configuration

Name: Radium Electron Configuration
Availability: InStock
Author: Nham Vu

Reference for radium's electron configuration (1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d¹⁰ 6s² 6p⁶ 7s²), orbital diagram, quantum numbers, and key properties.

Z = 88 Ra Radium

Radium — Electron Configuration

Atomic number 88 · Radioactive alkaline earth metal · Period 7, Group 2 · s-block

[Rn] 7s² 88 electrons 2 valence e⁻ +2 oxidation state

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
7s	s orbital, shell n=7	2	2	7s²
Total		88

Full Configuration

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

All 16 subshells written explicitly — 88 electrons total.

Noble-Gas Shorthand

[Rn] 7s²

[Rn] = 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d¹⁰ 6s² 6p⁶ (86 electrons).

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 7 (n=7) — 7s² 2 / 98 electrons (2%)

Shell 4 is fully filled (32 electrons). Shell 5 holds 18 of a possible 50. Shell 6 holds 8 of 72, and Shell 7 holds only the 2 valence electrons.

Orbital Box Diagram

Each box = one orbital. Paired arrows = opposite spins (+½ up, −½ down). All inner subshells are fully filled.

filled

valence electrons (paired, 7s²)

Opposing arrows represent paired electrons with opposite spins (+½ and −½). All subshells of radium are fully paired — it is diamagnetic with no unpaired electrons.

Quantum Numbers — Valence Electrons (7s²)

Electron #	n	l	mₗ	mₛ	Subshell
87	7	0	0	+½	7s
88	7	0	0	−½	7s

n = principal; l = azimuthal (0 = s subshell); mₗ = magnetic; mₛ = spin. Inner 86 electrons follow the same pattern for their respective subshells.

Summary

Reference for radium's electron configuration (1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d¹⁰ 6s² 6p⁶ 7s²), orbital diagram, quantum numbers, and key properties.

How it works

The Aufbau principle fills subshells from lowest to highest energy (1s → 2s → 2p → ... → 7s).
Radium's 88 electrons fill sixteen subshells across seven principal shells.
The 4f and 5d subshells — each carrying 14 and 10 electrons respectively — are the lanthanide- and d-block contributions that separate radium from lighter alkaline earth metals.
The outermost subshell is 7s², giving radium 2 valence electrons and a +2 oxidation state.
Noble-gas notation compresses the inner 86 electrons into [Rn], exposing only the valence 7s².
The three tabs let you explore the subshell table, orbital box diagram, and element facts separately.

Use cases

Quick reference for chemistry homework or exam prep on Period 7 elements.
Visualize how the 4f and 5d subshells fill before the 7s in the heaviest alkaline earth metal.
Understand why radium always forms a +2 ion by losing both 7s electrons.
Compare radium to lighter Group 2 members — barium, strontium, calcium — to see periodic trends.
Study how the radon noble-gas core stabilizes radium's inner electron structure.
Teaching aid for radioactivity, atomic structure, and s-block chemistry lessons.
Verify quantum numbers for radium's two valence electrons.

Frequently Asked Questions

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