What is the electron configuration of krypton?

Krypton (Kr, Z=36) has the ground-state electron configuration 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶. Its 36 electrons fill eight subshells across four principal shells.

What is the noble-gas shorthand for krypton?

The condensed notation is [Ar] 3d¹⁰ 4s² 4p⁶, where [Ar] represents the filled 1s² 2s² 2p⁶ 3s² 3p⁶ core shared with argon.

How many valence electrons does krypton have?

Krypton has 8 valence electrons: 2 in the 4s subshell and 6 in the 4p subshell. The complete 4s² 4p⁶ shell is why krypton is chemically inert.

Why is krypton chemically inert?

Krypton's outermost shell (n=4) is completely filled — 4s² 4p⁶ gives 8 valence electrons with no vacancies and no tendency to gain or lose electrons. This full outer shell means no net electrostatic drive to form bonds under ordinary conditions.

What does [Kr] mean in electron configurations?

[Kr] is the noble-gas shorthand used for period 5 elements (rubidium through xenon). It represents krypton's full configuration (1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶) as a condensed inner-core block.

What block and period is krypton in?

Krypton is in Period 4, Group 18, and belongs to the p-block of the periodic table. It is the heaviest of the "light" noble gases, heavier than argon but lighter than xenon.

Does krypton form any compounds?

Krypton is largely inert but can form compounds under extreme conditions. KrF₂ (krypton difluoride) is the best-documented, formed by reacting krypton with fluorine at very low temperatures under UV radiation. It is unstable at room temperature.

Krypton Electron Configuration

Name: Krypton Electron Configuration
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Author: Nham Vu

Reference for krypton's electron configuration (1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶), orbital diagram, quantum numbers, and key atomic properties.

Z = 36 Kr Krypton

Krypton — Electron Configuration

Atomic number 36 · Noble gas · Period 4, Group 18 · p-block

1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ [Ar] 3d¹⁰ 4s² 4p⁶ 36 electrons 8 valence e⁻

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 (valence)	6	6	4p⁶
Total		36

Full Configuration

1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶

All subshells written explicitly — 36 electrons total.

Noble-Gas Shorthand

[Ar] 3d¹⁰ 4s² 4p⁶

[Ar] = 1s² 2s² 2p⁶ 3s² 3p⁶ (the filled argon core, 18 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 8 / 32 electrons (25%)

Shell 4 can hold up to 32 electrons (4s + 4p + 4d + 4f). Krypton uses only 8 of those slots (4s² 4p⁶), leaving 4d and 4f unfilled. The filled 4s² 4p⁶ valence shell makes krypton a noble gas.

Orbital Box Diagram

2 electrons (paired) — filled

6 electrons across 3 orbitals — filled

2 electrons (paired) — filled

6 electrons across 3 orbitals — filled

10 electrons across 5 orbitals — filled

2 electrons (paired) — filled

6 electrons across 3 orbitals — filled (valence)

Each box represents one orbital. Opposing arrows show paired electrons with opposite spins (+½ and −½). Every orbital in krypton is completely filled — all 9 subshells at capacity — which is the defining feature of a noble gas. The 4p orbitals (highlighted border) form the valence shell.

Quantum Numbers — All 36 Electrons

e⁻ #	n	l	mₗ	mₛ	Subshell
1	1	0	0	+½	1s
2	1	0	0	−½	1s
3	2	0	0	+½	2s
4	2	0	0	−½	2s
5	2	1	-1	+½	2p
6	2	1	-1	−½	2p
7	2	1	0	+½	2p
8	2	1	0	−½	2p
9	2	1	1	+½	2p
10	2	1	1	−½	2p
11	3	0	0	+½	3s
12	3	0	0	−½	3s
13	3	1	-1	+½	3p
14	3	1	-1	−½	3p
15	3	1	0	+½	3p
16	3	1	0	−½	3p
17	3	1	1	+½	3p
18	3	1	1	−½	3p
19	3	2	-2	+½	3d
20	3	2	-2	−½	3d
21	3	2	-1	+½	3d
22	3	2	-1	−½	3d
23	3	2	0	+½	3d
24	3	2	0	−½	3d
25	3	2	1	+½	3d
26	3	2	1	−½	3d
27	3	2	2	+½	3d
28	3	2	2	−½	3d
29	4	0	0	+½	4s
30	4	0	0	−½	4s
31	4	1	-1	+½	4p
32	4	1	-1	−½	4p
33	4	1	0	+½	4p
34	4	1	0	−½	4p
35	4	1	1	+½	4p
36	4	1	1	−½	4p

n = principal; l = azimuthal (0→s, 1→p, 2→d); mₗ = magnetic; mₛ = spin. Electrons 29–36 (bold) are in the n=4 valence shell.

Summary

Reference for krypton's electron configuration (1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶), orbital diagram, quantum numbers, and key atomic properties.

How it works

The Aufbau principle fills orbitals from lowest to highest energy.
Krypton's 36 electrons fill nine subshells: 1s, 2s, 2p, 3s, 3p, 3d, 4s, and 4p.
The 3d subshell holds 10 electrons across five orbitals, all fully paired.
The 4p subshell holds 6 electrons across three orbitals — all pair-filled, completing krypton's valence shell.
Noble-gas notation replaces the inner filled shells with the nearest noble-gas in brackets: [Ar] 3d¹⁰ 4s² 4p⁶.
Because all subshells are completely filled, krypton is chemically inert and a noble gas (Group 18).

Use cases

Quick reference for chemistry homework on d-block filling and noble-gas configurations.
Understand why krypton defines the [Kr] abbreviated notation used for period 5 elements (Rb through Xe).
Compare krypton to neighboring elements bromine and rubidium in Period 4.
Visualize how a full 4p⁶ valence shell produces chemical inertness.
Teaching aid for the Aufbau principle, showing s, p, and d subshell filling in Period 4.
Verify quantum numbers for each of krypton's 36 electrons.

Frequently Asked Questions

Last updated: 2026-07-08 · Reviewed by Nham Vu

Krypton Electron Configuration

Krypton — Electron Configuration

Subshell Breakdown

Shell Fill Summary

Orbital Box Diagram

Quantum Numbers — All 36 Electrons

Identity

Physical Properties

Electronic Properties

Context & Uses

Summary

How it works

Use cases

Frequently Asked Questions

What is the electron configuration of krypton?

What is the noble-gas shorthand for krypton?

How many valence electrons does krypton have?

Why is krypton chemically inert?

What does [Kr] mean in electron configurations?

What block and period is krypton in?

Does krypton form any compounds?