Science & Chemistry

Electron Configuration Chart

Compare neutral ground-state configurations, orbital filling order, subshell capacities, noble-gas shorthand, common exceptions, ion configurations, and valence patterns. The chart uses observed configurations where the simple Aufbau prediction and the measured ground state differ.

Electron configuration is a quantum-mechanical orbital-occupancy description. It does not show electrons moving on fixed planetary paths, and introductory filling mnemonics do not replace evaluated ground-state data.

Electron Configuration Chart showing orbital filling order, subshell capacities, noble-gas notation, common exceptions, and ions

How electron configurations work

An electron configuration states how electrons occupy atomic orbitals. IUPAC defines it as the distribution of electrons over one-electron orbitals subject to the Pauli principle. A neutral atom contains the same number of electrons as its atomic number; an ion has fewer electrons when positively charged and more when negatively charged. See the IUPAC definition.

Each orbital holds at most two electrons. An s subshell contains one orbital, p contains three, d contains five, and f contains seven, so their capacities are 2, 6, 10, and 14 electrons. Hund's rule fills equal-energy orbitals singly before pairing, while noble-gas notation shortens the filled inner core.

Meaning

Electrons in orbitals

Electron configuration records how an atom or ion distributes electrons among occupied orbitals and subshells.

Subshell limits

s² · p⁶ · d¹⁰ · f¹⁴

One orbital holds at most two electrons, giving s, p, d, and f capacities of 2, 6, 10, and 14.

Prediction model

Aufbau + Hund + Pauli

These rules build most introductory configurations, but measured ground states include important exceptions.

Short form

[noble gas] + outer electrons

Noble-gas notation replaces a filled inner core with the preceding noble-gas symbol in brackets.

The usual filling sequence correctly predicts many atoms, but chromium is [Ar] 3d⁵ 4s¹ and copper is [Ar] 3d¹⁰ 4s¹. Those are observed neutral ground states, not errors in the table. NIST's evaluated compilation should take priority over a simplified diagonal-rule prediction. See NIST electron configurations.

Electron Configuration Chart for Elements 1–36

Neutral ground-state configurations from hydrogen through krypton. Chromium and copper show observed configurations that differ from the simplest diagonal-filling prediction.

Swipe horizontally inside the table to view every column.

Neutral ground-state configurations from hydrogen through krypton. Chromium and copper show observed configurations that differ from the simplest diagonal-filling prediction.
Z	Element	Symbol	Ground-state configuration	Noble-gas notation
1	Hydrogen	H	1s¹	1s¹
2	Helium	He	1s²	1s²
3	Lithium	Li	1s² 2s¹	[He] 2s¹
4	Beryllium	Be	1s² 2s²	[He] 2s²
5	Boron	B	1s² 2s² 2p¹	[He] 2s² 2p¹
6	Carbon	C	1s² 2s² 2p²	[He] 2s² 2p²
7	Nitrogen	N	1s² 2s² 2p³	[He] 2s² 2p³
8	Oxygen	O	1s² 2s² 2p⁴	[He] 2s² 2p⁴
9	Fluorine	F	1s² 2s² 2p⁵	[He] 2s² 2p⁵
10	Neon	Ne	1s² 2s² 2p⁶	[He] 2s² 2p⁶
11	Sodium	Na	1s² 2s² 2p⁶ 3s¹	[Ne] 3s¹
12	Magnesium	Mg	1s² 2s² 2p⁶ 3s²	[Ne] 3s²
13	Aluminium	Al	1s² 2s² 2p⁶ 3s² 3p¹	[Ne] 3s² 3p¹
14	Silicon	Si	1s² 2s² 2p⁶ 3s² 3p²	[Ne] 3s² 3p²
15	Phosphorus	P	1s² 2s² 2p⁶ 3s² 3p³	[Ne] 3s² 3p³
16	Sulfur	S	1s² 2s² 2p⁶ 3s² 3p⁴	[Ne] 3s² 3p⁴
17	Chlorine	Cl	1s² 2s² 2p⁶ 3s² 3p⁵	[Ne] 3s² 3p⁵
18	Argon	Ar	1s² 2s² 2p⁶ 3s² 3p⁶	[Ne] 3s² 3p⁶
19	Potassium	K	[Ar] 4s¹	[Ar] 4s¹
20	Calcium	Ca	[Ar] 4s²	[Ar] 4s²
21	Scandium	Sc	[Ar] 3d¹ 4s²	[Ar] 3d¹ 4s²
22	Titanium	Ti	[Ar] 3d² 4s²	[Ar] 3d² 4s²
23	Vanadium	V	[Ar] 3d³ 4s²	[Ar] 3d³ 4s²
24	Chromium	Cr	[Ar] 3d⁵ 4s¹ — Observed chromium exception	[Ar] 3d⁵ 4s¹
25	Manganese	Mn	[Ar] 3d⁵ 4s²	[Ar] 3d⁵ 4s²
26	Iron	Fe	[Ar] 3d⁶ 4s²	[Ar] 3d⁶ 4s²
27	Cobalt	Co	[Ar] 3d⁷ 4s²	[Ar] 3d⁷ 4s²
28	Nickel	Ni	[Ar] 3d⁸ 4s²	[Ar] 3d⁸ 4s²
29	Copper	Cu	[Ar] 3d¹⁰ 4s¹ — Observed copper exception	[Ar] 3d¹⁰ 4s¹
30	Zinc	Zn	[Ar] 3d¹⁰ 4s²	[Ar] 3d¹⁰ 4s²
31	Gallium	Ga	[Ar] 3d¹⁰ 4s² 4p¹	[Ar] 3d¹⁰ 4s² 4p¹
32	Germanium	Ge	[Ar] 3d¹⁰ 4s² 4p²	[Ar] 3d¹⁰ 4s² 4p²
33	Arsenic	As	[Ar] 3d¹⁰ 4s² 4p³	[Ar] 3d¹⁰ 4s² 4p³
34	Selenium	Se	[Ar] 3d¹⁰ 4s² 4p⁴	[Ar] 3d¹⁰ 4s² 4p⁴
35	Bromine	Br	[Ar] 3d¹⁰ 4s² 4p⁵	[Ar] 3d¹⁰ 4s² 4p⁵
36	Krypton	Kr	[Ar] 3d¹⁰ 4s² 4p⁶	[Ar] 3d¹⁰ 4s² 4p⁶

Superscripts give electron counts in each occupied subshell.

• These are neutral ground-state configurations.
• NIST is the reference for observed ground-state configurations; simple filling rules are a model and have exceptions.

Table sources: National Institute of Standards and Technology — Electronic Configurations of the Elements

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Subshell and Orbital Capacity Chart

Each orbital can hold at most two electrons. The number of orbitals in a subshell determines its total capacity.

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Each orbital can hold at most two electrons. The number of orbitals in a subshell determines its total capacity.
Subshell	Angular momentum l	Orbitals	Maximum electrons	Typical notation
s	0	1	2	s²
p	1	3	6	p⁶
d	2	5	10	d¹⁰
f	3	7	14	f¹⁴

Maximum electrons = 2 × number of orbitals.

• Pauli exclusion limits each orbital to two electrons with opposite spin.
• Subshell capacity does not mean every subshell is filled in every ground state.

Table sources: International Union of Pure and Applied Chemistry — Gold Book — electron configuration

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Aufbau Orbital Filling Order Chart

The common Aufbau sequence is useful for predicting many ground-state configurations, but observed atomic configurations can differ when subshell energies are very close.

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The common Aufbau sequence is useful for predicting many ground-state configurations, but observed atomic configurations can differ when subshell energies are very close.
Step	Subshell	Capacity	Cumulative capacity if filled
1	1s	2	2
2	2s	2	4
3	2p	6	10
4	3s	2	12
5	3p	6	18
6	4s	2	20
7	3d	10	30
8	4p	6	36
9	5s	2	38
10	4d	10	48
11	5p	6	54
12	6s	2	56
13	4f	14	70
14	5d	10	80
15	6p	6	86
16	7s	2	88
17	5f	14	102
18	6d	10	112
19	7p	6	118

Sequence used as a practical filling model.

• Do not use this sequence as proof that every observed ground state follows it exactly.
• For transition-metal cations, electron removal order is not simply the reverse of this list.

Table sources: National Institute of Standards and Technology — Electronic Configurations of the Elements; International Union of Pure and Applied Chemistry — Gold Book — electron configuration

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The superscripts must add to the electron count

Carbon has six electrons, so 1s² 2s² 2p² totals 6. Chloride has 18 electrons because neutral chlorine has 17 and Cl⁻ has gained one. Counting superscripts is the fastest way to catch many configuration mistakes before checking orbital order.

Noble-Gas Core Notation Chart

Bracket notation replaces a completed noble-gas core with its element symbol, making long configurations easier to read.

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Bracket notation replaces a completed noble-gas core with its element symbol, making long configurations easier to read.
Core	Atomic number	Full closed-shell configuration	Example use
[He]	2	1s²	Li = [He] 2s¹
[Ne]	10	1s² 2s² 2p⁶	Na = [Ne] 3s¹
[Ar]	18	[Ne] 3s² 3p⁶	Fe = [Ar] 3d⁶ 4s²
[Kr]	36	[Ar] 3d¹⁰ 4s² 4p⁶	Mo = [Kr] 4d⁵ 5s¹
[Xe]	54	[Kr] 4d¹⁰ 5s² 5p⁶	Au = [Xe] 4f¹⁴ 5d¹⁰ 6s¹
[Rn]	86	[Xe] 4f¹⁴ 5d¹⁰ 6s² 6p⁶	Used as the core for many actinides

Bracketed symbol means all electrons of that noble-gas ground-state core are included.

• Use the preceding noble gas, not the nearest noble gas after the element.
• NIST uses bracketed rare-gas symbols to shorten heavier configurations.

Table sources: National Institute of Standards and Technology — Ground Levels and Ionization Energies for the Neutral Atoms; National Institute of Standards and Technology — Electronic Configurations of the Elements

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Common Ground-State Configuration Exceptions

Several atoms have observed ground states that differ from the simplest Aufbau prediction because nearby subshells have similar energies.

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Several atoms have observed ground states that differ from the simplest Aufbau prediction because nearby subshells have similar energies.
Element	Simple prediction	Observed ground state	Pattern to remember
Chromium (Cr)	[Ar] 3d⁴ 4s²	[Ar] 3d⁵ 4s¹	Half-filled 3d in the observed ground state
Copper (Cu)	[Ar] 3d⁹ 4s²	[Ar] 3d¹⁰ 4s¹	Filled 3d in the observed ground state
Niobium (Nb)	[Kr] 4d³ 5s²	[Kr] 4d⁴ 5s¹	Observed redistribution between 4d and 5s
Molybdenum (Mo)	[Kr] 4d⁴ 5s²	[Kr] 4d⁵ 5s¹	Half-filled 4d
Ruthenium (Ru)	[Kr] 4d⁶ 5s²	[Kr] 4d⁷ 5s¹	Observed 4d/5s redistribution
Rhodium (Rh)	[Kr] 4d⁷ 5s²	[Kr] 4d⁸ 5s¹	Observed 4d/5s redistribution
Palladium (Pd)	[Kr] 4d⁸ 5s²	[Kr] 4d¹⁰	Filled 4d; 5s is empty in the ground state
Platinum (Pt)	[Xe] 4f¹⁴ 5d⁸ 6s²	[Xe] 4f¹⁴ 5d⁹ 6s¹	Observed 5d/6s redistribution
Gold (Au)	[Xe] 4f¹⁴ 5d⁹ 6s²	[Xe] 4f¹⁴ 5d¹⁰ 6s¹	Filled 5d in the observed ground state

Observed neutral ground-state configurations.

• Treat these as observed configurations, not as a universal “half-filled/full-filled rule.”
• Heavier atoms can require more detailed relativistic and spectroscopic treatment.

Table sources: National Institute of Standards and Technology — Electronic Configurations of the Elements

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Aufbau is a model, not an exception-free law

Subshell energies can be close enough that the lowest-energy many-electron arrangement differs from the simplest mnemonic. NIST lists chromium as [Ar] 3d⁵ 4s¹, copper as [Ar] 3d¹⁰ 4s¹, palladium as [Kr] 4d¹⁰, platinum as [Xe] 4f¹⁴ 5d⁹ 6s¹, and gold as [Xe] 4f¹⁴ 5d¹⁰ 6s¹.

Electron Configuration Finder

Choose atomic number 1–36 to see the observed neutral ground-state configuration used by this chart. Chromium and copper use their measured ground-state exceptions rather than the simplest Aufbau prediction.

Atomic number

Z = 24

Chromium (Cr)

Ground-state configuration: [Ar] 3d⁵ 4s¹
Noble-gas notation: [Ar] 3d⁵ 4s¹
Electrons by principal shell: 2, 8, 13, 1
Electrons outside listed noble-gas core: 6

The finder reports neutral atoms only. Ion configurations require adding or removing electrons from the neutral ground state using ion-specific rules.

Common Ion Electron Configuration Chart

Main-group ions often reach a noble-gas configuration. Transition-metal cations generally lose the outer ns electrons before electrons from the (n−1)d subshell.

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Main-group ions often reach a noble-gas configuration. Transition-metal cations generally lose the outer ns electrons before electrons from the (n−1)d subshell.
Species	Neutral atom	Electrons added / removed	Ion configuration
Na⁺	[Ne] 3s¹	Remove 1 from 3s	[Ne]
Mg²⁺	[Ne] 3s²	Remove 2 from 3s	[Ne]
Al³⁺	[Ne] 3s² 3p¹	Remove 3 from n = 3	[Ne]
O²⁻	[He] 2s² 2p⁴	Add 2 to 2p	[Ne]
Cl⁻	[Ne] 3s² 3p⁵	Add 1 to 3p	[Ar]
Ca²⁺	[Ar] 4s²	Remove 2 from 4s	[Ar]
Cr³⁺	[Ar] 3d⁵ 4s¹	Remove 4s¹, then 2 from 3d	[Ar] 3d³
Mn²⁺	[Ar] 3d⁵ 4s²	Remove 2 from 4s	[Ar] 3d⁵
Fe²⁺	[Ar] 3d⁶ 4s²	Remove 2 from 4s	[Ar] 3d⁶
Fe³⁺	[Ar] 3d⁶ 4s²	Remove 2 from 4s, then 1 from 3d	[Ar] 3d⁵
Cu⁺	[Ar] 3d¹⁰ 4s¹	Remove 1 from 4s	[Ar] 3d¹⁰
Cu²⁺	[Ar] 3d¹⁰ 4s¹	Remove 4s¹, then 1 from 3d	[Ar] 3d⁹
Zn²⁺	[Ar] 3d¹⁰ 4s²	Remove 2 from 4s	[Ar] 3d¹⁰

Ground-state electron counts for common monatomic ions.

• For transition metals, remove electrons from the highest principal quantum number ns subshell before (n−1)d.
• An ion configuration is not obtained by blindly reversing the neutral filling sequence.

Table sources: National Institute of Standards and Technology — Electronic Configurations of the Elements

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Transition-metal ions lose ns electrons before (n−1)d electrons

Iron is [Ar] 3d⁶ 4s², but Fe²⁺ is [Ar] 3d⁶ because the two 4s electrons are removed first. Fe³⁺ is then [Ar] 3d⁵. Copper follows the same removal logic from its observed neutral ground state: Cu⁺ is [Ar] 3d¹⁰ and Cu²⁺ is [Ar] 3d⁹.

Orbital Box Rules Chart

Orbital diagrams add electron spin and orbital occupancy to the configuration notation.

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Orbital diagrams add electron spin and orbital occupancy to the configuration notation.
Rule	Meaning	Example	Common mistake
Pauli exclusion	Maximum two electrons per orbital with opposite spins	1s² = ↑↓	Putting three electrons in one orbital
Hund rule	Fill degenerate orbitals singly before pairing	2p³ = ↑ ↑ ↑	Pairing in one p orbital too early
Aufbau principle	Occupy lower-energy orbitals first as a starting model	1s before 2s before 2p	Assuming the simple order has no exceptions
Electron count	Superscripts must sum to the species electron total	Fe: 26 electrons	Forgetting ionic charge changes electron count
Degeneracy	p, d, f contain 3, 5, 7 orbitals respectively	d has five boxes	Drawing one box for an entire d subshell

Arrow direction represents spin projection in orbital-box notation.

• Orbital boxes are a representation of one-electron orbitals and occupancies, not literal electron paths.

Table sources: International Union of Pure and Applied Chemistry — Gold Book — electron configuration

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Main-Group Valence Configuration Patterns

For representative main-group elements, the outer-shell ns and np pattern tracks the group and helps predict common bonding behavior.

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For representative main-group elements, the outer-shell ns and np pattern tracks the group and helps predict common bonding behavior.
Group	Outer configuration pattern	Typical valence electrons	Example
1	ns¹	1	Na: [Ne] 3s¹
2	ns²	2	Mg: [Ne] 3s²
13	ns² np¹	3	Al: [Ne] 3s² 3p¹
14	ns² np²	4	Si: [Ne] 3s² 3p²
15	ns² np³	5	P: [Ne] 3s² 3p³
16	ns² np⁴	6	S: [Ne] 3s² 3p⁴
17	ns² np⁵	7	Cl: [Ne] 3s² 3p⁵
18	ns² np⁶	8	Ar: [Ne] 3s² 3p⁶

Helium is the main exception to the ns²np⁶ noble-gas pattern because its shell contains only 1s².

• Transition-metal valence counting is more context dependent because both ns and (n−1)d electrons can participate in chemistry.

Table sources: National Institute of Standards and Technology — Electronic Configurations of the Elements

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Principal Shell Capacity and Subshell Chart

A principal shell with quantum number n can contain up to 2n² electrons, but ground-state atoms do not simply fill one shell completely before beginning the next.

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A principal shell with quantum number n can contain up to 2n² electrons, but ground-state atoms do not simply fill one shell completely before beginning the next.
Shell n	Available subshells	Maximum shell capacity 2n²	Important note
1	1s	2	Only the s subshell exists
2	2s, 2p	8	Second-period elements fill these subshells
3	3s, 3p, 3d	18	4s begins filling before 3d in the common Aufbau sequence
4	4s, 4p, 4d, 4f	32	Several n = 4 subshells fill across different periods
5	5s, 5p, 5d, 5f, 5g	50	The g subshell is part of the mathematical shell even though ordinary ground-state tables focus on lower-l subshells
6	6s, 6p, 6d, 6f, 6g, 6h	72	Known ground states use only part of this mathematical capacity
7	7s, 7p, 7d, 7f, 7g, 7h, 7i	98	High-n orbital ordering becomes increasingly complex

Maximum capacity of a complete principal shell = 2n².

• The 2n² rule is a shell capacity rule, not a step-by-step filling order.

Table sources: International Union of Pure and Applied Chemistry — Gold Book — electron configuration

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Common Electron Configuration Errors and Corrections

Most configuration errors come from incorrect electron totals, subshell capacities, ion removal order, or treating the Aufbau sequence as exception free.

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Most configuration errors come from incorrect electron totals, subshell capacities, ion removal order, or treating the Aufbau sequence as exception free.
Mistake	Why it fails	Better approach
Write p⁷	A p subshell has only three orbitals and holds at most six electrons	Move the next electron to the next available subshell
Write d¹¹	A d subshell has five orbitals and holds at most ten electrons	Respect the d¹⁰ capacity
Use [Ar] 3d⁴ 4s² for chromium	That is the simplest prediction, not the observed neutral ground state	Use [Ar] 3d⁵ 4s¹
Use [Ar] 3d⁹ 4s² for copper	That is not the observed neutral ground state	Use [Ar] 3d¹⁰ 4s¹
Remove 3d electrons before 4s for Fe²⁺	Transition-metal cations lose the higher-n 4s electrons first	Fe²⁺ = [Ar] 3d⁶
Forget charge when counting electrons	Ions do not have Z electrons unless neutral	Electron count = Z − positive charge or Z + magnitude of negative charge
Choose the next noble gas in shorthand	That would include electrons the atom does not have	Use the preceding noble-gas core
Treat orbital boxes as electron trajectories	Orbitals are quantum states, not little planetary paths	Use boxes only to represent occupancy and spin
Call every outer-shell electron “the only valence electron” in transition metals	d electrons can participate in transition-metal chemistry	State the valence convention being used
Assume excited-state configurations equal ground states	Promoted electrons describe a different electronic state	Label excited states explicitly

Checklist for neutral atoms, ions, and orbital diagrams.

• When a reference table and a simple mnemonic disagree, use evaluated observed ground-state data for the atom in question.

Table sources: National Institute of Standards and Technology — Electronic Configurations of the Elements; International Union of Pure and Applied Chemistry — Gold Book — electron configuration

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Ground state and excited state are not interchangeable

A ground-state configuration gives the lowest-energy arrangement for the specified species. An excited state promotes one or more electrons into a higher-energy orbital. When a problem asks for the electron configuration without another qualifier, use the ground state unless the context explicitly describes excitation.

NIST's periodic table incorporates critically evaluated atomic data including ground-state configurations, which makes it a stronger reference than a hand-drawn diagonal mnemonic when exact configurations matter. See the NIST periodic table reference.

Frequently asked questions

What is an electron configuration?

An electron configuration describes how electrons are distributed among atomic orbitals. The superscripts show how many electrons occupy each subshell.

How many electrons fit in s, p, d, and f subshells?

An s subshell holds 2 electrons, p holds 6, d holds 10, and f holds 14.

What is the Aufbau filling order?

A common sequence is 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p. Observed ground states include exceptions.

Why is chromium [Ar] 3d5 4s1?

The observed chromium ground state is [Ar] 3d⁵ 4s¹ rather than the simplest [Ar] 3d⁴ 4s² prediction because the 3d and 4s energies are close and the actual many-electron ground state is lower in energy.

Why is copper [Ar] 3d10 4s1?

Copper has the observed ground-state configuration [Ar] 3d¹⁰ 4s¹. It is another case where the simplest diagonal-filling prediction does not match the measured ground state.

What does noble-gas notation mean?

Noble-gas notation replaces the filled inner-shell configuration with the symbol of the preceding noble gas in brackets, such as Fe = [Ar] 3d⁶ 4s².

How do I find the electron configuration of an ion?

Start from the neutral ground-state configuration, adjust the electron count for charge, and remove or add electrons using the correct orbital order for that ion.

Why are 4s electrons removed before 3d electrons?

Although 4s is occupied before 3d in the usual neutral-atom filling sequence, transition-metal cations generally lose the higher-principal-quantum-number 4s electrons before 3d electrons.

What is Hund rule?

Hund rule says degenerate orbitals are occupied singly with parallel spin before electrons pair in the same orbital.

What is the Pauli exclusion principle?

No two electrons in one atom can have the same complete set of quantum numbers, so one orbital holds at most two electrons with opposite spin.

How many orbitals are in p, d, and f subshells?

A p subshell has 3 orbitals, d has 5, and f has 7.

How do I check an electron configuration?

Add every superscript and confirm the total equals the species electron count, then verify subshell capacities and any known ground-state exception.

Are valence electrons always the electrons in the highest shell?

That shortcut works well for many main-group elements, but transition-metal chemistry can also involve electrons from the partially filled d subshell.

Is the Aufbau rule exact?

No. It is a useful orbital-filling model, but evaluated ground-state configurations show multiple exceptions where near-degenerate subshells redistribute electrons.

Does an electron configuration show where an electron physically is?

No. It specifies orbital occupancy in a quantum-mechanical description; it does not trace a classical path around the nucleus.

What is an excited-state electron configuration?

An excited-state configuration has one or more electrons promoted above the ground-state arrangement. It must be identified separately from the ground state.

Use the Atomic Radius Chart to connect electronic structure with periodic size trends, the Codon Chart for molecular-biology notation, or the Density Chart for physical-property reference data.

Sources

International Union of Pure and Applied Chemistry — Gold Book — electron configuration

Defines electron configuration as the distribution of electrons over one-electron orbitals subject to the Pauli principle.

https://goldbook.iupac.org/terms/view/C01248

National Institute of Standards and Technology — Electronic Configurations of the Elements

Provides evaluated neutral ground-state electron configurations and first-cation configurations for elements through uranium.

https://www.nist.gov/pml/atomic-reference-data-electronic-structure-calculations/atomic-reference-data-electronic-8

National Institute of Standards and Technology — Periodic Table of the Elements

NIST periodic table with critically evaluated atomic data including ground-state configuration.

https://www.nist.gov/publications/periodic-table-elements-0

National Institute of Standards and Technology — Ground Levels and Ionization Energies for the Neutral Atoms

Explains NIST ground-state configuration notation and noble-gas abbreviation in atomic data tables.

https://www.nist.gov/pml/ground-levels-and-ionization-energies-neutral-atoms

Step	Subshell	Capacity	Cumulative capacity if filled
1	1s	2	2
2	2s	2	4
3	2p	6	10
4	3s	2	12
5	3p	6	18
6	4s	2	20
7	3d	10	30
8	4p	6	36
9	5s	2	38
10	4d	10	48
11	5p	6	54
12	6s	2	56
13	4f	14	70
14	5d	10	80
15	6p	6	86
16	7s	2	88
17	5f	14	102
18	6d	10	112
19	7p	6	118

Step	Subshell	Capacity	Cumulative capacity if filled
1	1s	2	2
2	2s	2	4
3	2p	6	10
4	3s	2	12
5	3p	6	18
6	4s	2	20
7	3d	10	30
8	4p	6	36
9	5s	2	38
10	4d	10	48
11	5p	6	54
12	6s	2	56
13	4f	14	70
14	5d	10	80
15	6p	6	86
16	7s	2	88
17	5f	14	102
18	6d	10	112
19	7p	6	118

How electron configurations work

Electron Configuration Chart for Elements 1–36

Subshell and Orbital Capacity Chart

Aufbau Orbital Filling Order Chart

The superscripts must add to the electron count

Noble-Gas Core Notation Chart

Common Ground-State Configuration Exceptions

Aufbau is a model, not an exception-free law

Electron Configuration Finder

Common Ion Electron Configuration Chart

Transition-metal ions lose ns electrons before (n−1)d electrons

Orbital Box Rules Chart

Main-Group Valence Configuration Patterns

Principal Shell Capacity and Subshell Chart

Common Electron Configuration Errors and Corrections

Ground state and excited state are not interchangeable

Frequently asked questions

Related ChartsLoom references

Sources

International Union of Pure and Applied Chemistry — Gold Book — electron configuration

National Institute of Standards and Technology — Electronic Configurations of the Elements

National Institute of Standards and Technology — Periodic Table of the Elements

National Institute of Standards and Technology — Ground Levels and Ionization Energies for the Neutral Atoms

Step	Subshell	Capacity	Cumulative capacity if filled
1	1s	2	2
2	2s	2	4
3	2p	6	10
4	3s	2	12
5	3p	6	18
6	4s	2	20
7	3d	10	30
8	4p	6	36
9	5s	2	38
10	4d	10	48
11	5p	6	54
12	6s	2	56
13	4f	14	70
14	5d	10	80
15	6p	6	86
16	7s	2	88
17	5f	14	102
18	6d	10	112
19	7p	6	118