What is the electron configuration of cadmium?

Cadmium (Cd, Z=48) has the ground-state electron configuration 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s². Its 48 electrons fill ten subshells across five principal shells.

What is the noble-gas shorthand for cadmium?

The condensed notation is [Kr] 4d¹⁰ 5s², where [Kr] represents the filled 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ core shared with krypton.

How many valence electrons does cadmium have?

Cadmium has 2 valence electrons in the 5s subshell. This is consistent with its Group 12 membership and its common +2 oxidation state, formed by losing both 5s electrons.

Why is cadmium sometimes not classified as a transition metal?

Cadmium's ground state and its most stable ion (Cd²⁺) both have completely filled d subshells (4d¹⁰). IUPAC defines transition metals as elements with an incomplete d subshell in their atom or common ions. By that strict definition, cadmium is a post-transition metal or Group 12 metal.

What oxidation states does cadmium form?

Cadmium almost exclusively shows a +2 oxidation state in its compounds (e.g., CdO, CdCl₂, CdS), formed by removing both 5s electrons. The Cd²⁺ ion retains the filled 4d¹⁰ configuration, which is particularly stable.

What block and period is cadmium in?

Cadmium is in Period 5, Group 12, and formally belongs to the d-block of the periodic table, sitting at the far right of the d-block row in Period 5.

How does cadmium's configuration compare to zinc?

Zinc (Z=30) is directly above cadmium in Group 12, with configuration [Ar] 3d¹⁰ 4s². Cadmium adds a filled 4p⁶ subshell and shifts to the 5s orbital, giving [Kr] 4d¹⁰ 5s². Both share the same valence configuration (d¹⁰ s²).

Yes. Cadmium and its compounds are highly toxic and classified as carcinogens. Industrial exposure occurs in battery manufacturing, electroplating, and pigment production. It accumulates in the kidneys and bones. Despite its toxicity, cadmium remains important in nickel-cadmium batteries and thin-film solar cells (CdTe).

Cadmium Electron Configuration

Name: Cadmium Electron Configuration
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Author: Nham Vu

Reference tool for cadmium's electron configuration (1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s²), orbital box diagram, quantum numbers, and key atomic properties.

Z = 48 Cd Cadmium

Cadmium — Electron Configuration

Atomic number 48 · Post-transition metal · Period 5, Group 12 · d-block

1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² [Kr] 4d¹⁰ 5s² 48 electrons 2 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	6	6	4p⁶
4d	d orbitals, shell n=4	10	10	4d¹⁰
5s	s orbital, shell n=5	2	2	5s²
Total		48

Full Configuration

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

All subshells written explicitly.

Noble-Gas Shorthand

[Kr] 4d¹⁰ 5s²

[Kr] = 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ (the filled krypton 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 18 / 32 electrons (56%)

Shell 5 (n=5) — 5s² 2 / 50 electrons (4%)

Shell 4 can hold up to 32 electrons (4s + 4p + 4d + 4f). Cadmium uses 18 of those slots. Shell 5 can hold up to 50 electrons; cadmium uses only 2.

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

10 electrons across 5 orbitals — filled

2 electrons (paired) — outermost (valence)

Each box represents one orbital. Opposing arrows show paired electrons (+½ and −½). Cadmium's two 5s valence electrons occupy the single 5s orbital in a paired state. All inner subshells, including 4d, are completely filled — giving cadmium its closed-shell stability.

Quantum Numbers for All 48 Electrons

Electron #	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
37	4	2	-2	+½	4d
38	4	2	-2	−½	4d
39	4	2	-1	+½	4d
40	4	2	-1	−½	4d
41	4	2	0	+½	4d
42	4	2	0	−½	4d
43	4	2	1	+½	4d
44	4	2	1	−½	4d
45	4	2	2	+½	4d
46	4	2	2	−½	4d
47	5	0	0	+½	5s
48	5	0	0	−½	5s

n = principal quantum number; l = azimuthal (l=0 → s, l=1 → p, l=2 → d); mₗ = magnetic; mₛ = spin. Electrons 47–48 occupy the 5s orbital with opposite spins, completing cadmium's ground-state configuration.

Summary

Reference tool for cadmium's electron configuration (1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s²), orbital box diagram, quantum numbers, and key atomic properties.

How it works

The Aufbau principle fills orbitals from lowest to highest energy.
Cadmium's 48 electrons fill ten subshells: 1s through 5s.
The 4d subshell holds 10 electrons across five orbitals, completing the d-block period.
The 5s subshell holds 2 electrons, giving cadmium its 2 valence electrons.
Noble-gas notation replaces the inner filled shells with krypton in brackets: [Kr] 4d¹⁰ 5s².
The tabs below let you explore the full configuration, orbital diagram, and element data separately.

Use cases

Quick reference for chemistry homework or exam review on d-block elements.
Understand why cadmium has a fully filled 4d subshell and sits at the end of the d-block.
Compare cadmium to zinc and mercury, its Group 12 neighbors above and below.
Verify that a fully filled d¹⁰ subshell gives cadmium closed-shell stability.
Teaching aid for Period 5 d-block electron filling and Group 12 chemistry.
Verify quantum numbers for each of cadmium's 48 electrons.
Explore how cadmium's +2 oxidation state results from losing both 5s electrons.

Frequently Asked Questions

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

Cadmium Electron Configuration

Cadmium — Electron Configuration

Subshell Breakdown

Shell Fill Summary

Orbital Box Diagram

Quantum Numbers for All 48 Electrons

Identity

Physical Properties

Electronic Properties

Context & Uses

Summary

How it works

Use cases

Frequently Asked Questions

What is the electron configuration of cadmium?

What is the noble-gas shorthand for cadmium?

How many valence electrons does cadmium have?

Why is cadmium sometimes not classified as a transition metal?

What oxidation states does cadmium form?

What block and period is cadmium in?

How does cadmium's configuration compare to zinc?

Is cadmium toxic?