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Electron Configuration Calculator

Chemistry

Find the ground-state electron configuration for any element. Shows full configuration, noble gas shorthand, valence electrons, period, group, and s/p/d/f block for all 118 elements.

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Full Electron Configuration

Element not found — enter symbol (Fe), atomic number (26), or name (Iron)
Noble Gas Shorthand
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Valence Electrons
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Period
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Group
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Block (s / p / d / f)
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This calculator computes your Full Electron Configuration, Noble Gas Shorthand, Valence Electrons, Period, Group, Block (s / p / d / f) from the values you enter.

Inputs
Element Symbol or Atomic Number
Outputs
Full Electron ConfigurationNoble Gas ShorthandValence ElectronsPeriodGroupBlock (s / p / d / f)

What is a Electron Config?

The Electron Configuration Calculator finds the ground-state electron configuration for any of the 118 elements. Enter a symbol (Fe), atomic number (26), or name (iron) and get the full configuration (1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁶ 4s²), noble gas shorthand ([Ar] 3d⁶ 4s²), valence electrons, period, group, and block (s/p/d/f).

All 118 elements are covered, including all Aufbau exceptions (Cr, Cu, Nb, Mo, Ru, Rh, Pd, Ag, La, Ce, Gd, Pt, Au, Ac, Th, Pa, U, Np, Cm, Lr, and heavy transactinides). The configurations are hardcoded from IUPAC and standard inorganic chemistry references — no Aufbau algorithm is used, so exceptions are correctly handled.

For the context of how electron configurations determine chemical bonding, the Bond Order Calculator uses molecular orbital theory, and the Effective Nuclear Charge Calculator uses Slater's rules on the electron configuration to find Zeff. The Electronegativity Calculator shows how Pauling electronegativities correlate with electron configurations across periods.

How to use this Electron Config calculator

  1. Enter the element symbol (Fe, Cu, Xe, U), atomic number (26, 29, 54, 92), or element name (iron, copper, xenon, uranium).
  2. The calculator resolves the query — case-insensitive for symbols and names.
  3. Read the Full Electron Configuration — copy for exam answers or lab notebooks.
  4. Read the Noble Gas Shorthand — the standard form for university and competitive exam use.
  5. Note Valence Electrons — count unpaired electrons for magnetic property prediction.
  6. Cross-reference Group with periodic table position for oxidation state trends.

Formula & Methodology

Electron filling order and shorthand notation:

Aufbau filling order: 1s → 2s → 2p → 3s → 3p → 4s → 3d → 4p → 5s → 4d → 5p → 6s → 4f → 5d → 6p → 7s → 5f → 6d → 7p  Maximum electrons per subshell:   s: 2 electrons (1 orbital)   p: 6 electrons (3 orbitals)   d: 10 electrons (5 orbitals)   f: 14 electrons (7 orbitals)  Noble gas shorthand:   Element config = [Noble gas core] + valence/sub-valence orbitals   [He] = 1s2   [Ne] = 1s2 2s2 2p6   [Ar] = 1s2 2s2 2p6 3s2 3p6   [Kr] = 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6   [Xe] = [Kr] + 4d10 5s2 5p6   [Rn] = [Xe] + 4f14 5d10 6s2 6p6

Worked example — Chromium (Cr, Z=24):

Predicted by Aufbau: [Ar] 3d⁴ 4s² — but this is incorrect.

Actual: [Ar] 3d⁵ 4s¹

Reason: half-filled 3d subshell (3d⁵) is extra stable (exchange energy) All five 3d orbitals singly occupied with same spin (Hund's rule) This lowers total energy below the predicted configuration  Full: 1s2 2s2 2p6 3s2 3p6 3d5 4s1 Shorthand: [Ar] 3d5 4s1 Valence electrons: 6 (d5 + s1) Period: 4, Group: 6, Block: d

Chromium is produced in India at FACOR (Ferro Alloys Corporation, Odisha) and Balasore Alloys — India is the world's 4th largest ferrochrome producer. Chromium's electron configuration ([Ar] 3d⁵ 4s¹) explains its variable oxidation states (+2, +3, +6) — Cr(VI) as K₂Cr₂O₇ is used in Indian tanneries (Kanpur) and electroplating industries (Pune, Chennai). Cr³⁺ gives the green colour to chrome oxide (Cr₂O₃), widely used in Indian pigment and paint manufacturing.

Frequently Asked Questions

Electron configuration is the distribution of electrons in an atom's atomic orbitals, written using the Aufbau notation: 1s², 2s², 2p⁶, 3s², etc. It determines an element's chemical properties — bonding behaviour, oxidation states, reactivity, and position in the periodic table. The electron configuration determines which electrons are available for chemical bonding (valence electrons) and how the atom interacts with other atoms. For iron (Fe, Z=26): [Ar] 3d⁶ 4s² — the 3d⁶ electrons explain why Fe has +2 and +3 oxidation states and why it forms coloured coordination compounds (all studied in Indian NCERT Class 12 d-block chapter).
Enter the element symbol (Fe), atomic number (26), or element name (iron / Iron) in the input field. The calculator looks up the ground-state electron configuration for all 118 elements and returns: full electron configuration (e.g., 1s2 2s2 2p6 3s2 3p6 3d6 4s2), noble gas shorthand ([Ar] 3d6 4s2), number of valence electrons, period, group, and block (s/p/d/f). Default: Fe (iron) — a key element in Indian steel production.
The Aufbau principle states that electrons fill orbitals in order of increasing energy: 1s → 2s → 2p → 3s → 3p → 4s → 3d → 4p → 5s → 4d → 5p → 6s → 4f → 5d → ... The mnemonics '1s 2s 2p 3s 3p 4s 3d 4p...' or the diagonal rule are standard in NCERT Class 11. Key exceptions: Cr (24): [Ar] 3d⁵ 4s¹ (not 3d⁴ 4s²) — half-filled 3d is extra stable. Cu (29): [Ar] 3d¹⁰ 4s¹ (not 3d⁹ 4s²) — fully filled 3d is extra stable. Similarly: Mo (42) = [Kr] 4d⁵ 5s¹; Ag (47) = [Kr] 4d¹⁰ 5s¹; Au (79) = [Xe] 4f¹⁴ 5d¹⁰ 6s¹; Pd (46) = [Kr] 4d¹⁰ (no 5s electron at all!). These exceptions appear in CBSE Class 12 and JEE Advanced chemistry.
Noble gas shorthand replaces the inner core electron configuration with the symbol of the preceding noble gas in brackets. This is the standard notation for JEE, NEET, and university chemistry. Example: Fe = 1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁶ 4s². The argon core (Z=18) = 1s² 2s² 2p⁶ 3s² 3p⁶. So Fe = [Ar] 3d⁶ 4s². Noble gas cores: [He] for period 2 elements; [Ne] for period 3; [Ar] for period 4; [Kr] for period 5; [Xe] for period 6; [Rn] for period 7. The noble gas shorthand highlights only the valence and sub-valence electrons — the chemically active part of the configuration.
Valence electrons are those in the outermost shell (highest principal quantum number n) — the electrons available for chemical bonding. For main group elements (s and p block), valence electrons = electrons in the highest n shell. Examples: Na [Ne] 3s¹ → 1 valence electron (Group 1). Cl [Ne] 3s² 3p⁵ → 7 valence electrons (Group 17). For d-block transition metals, valence electrons include the (n-1)d and ns electrons. Fe [Ar] 3d⁶ 4s² → 8 valence electrons. For f-block (lanthanides/actinides), the 4f or 5f electrons plus the outer s and d electrons are all considered. The number of valence electrons determines an element's position in the periodic table group and its typical number of bonds.
Blocks in the periodic table are defined by which orbital the last electron enters: s-block (Groups 1–2): outermost electron enters an s orbital. H, He, alkali metals, alkaline earth metals. p-block (Groups 13–18): outermost electron enters a p orbital. Includes most nonmetals, halogens, noble gases, and some metalloids. d-block (Groups 3–12): last electron enters a d orbital. All transition metals (Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, and 4th/5th/6th row equivalents). f-block (groups not numbered): last electron enters an f orbital. Lanthanides (Ce–Lu) and actinides (Th–Lr). Indian NCERT: d-block in Class 12 Chapter 8; f-block (lanthanides/actinides) at end of the same chapter. TIFR Mumbai, IISc Bangalore, and Bhabha Atomic Research Centre (BARC) study f-block elements including uranium and thorium.
Electron configurations appear in JEE Advanced and NEET in several contexts: Identifying exceptions to Aufbau principle (Cr, Cu, Mo, Ag, Au — high-value MCQ topic). Predicting oxidation states: elements with [noble gas] d¹⁰ configurations (Cu, Zn) commonly show +1 or +2. Magnetic properties: unpaired electrons → paramagnetic; all paired → diamagnetic. Fe: [Ar] 3d⁶ 4s² → 4 unpaired electrons → strongly paramagnetic. Identifying block and period from configuration. Bond formation: number of unpaired electrons in ground or excited state determines covalency (hybridization). Indian NCERT Class 11 Chapter 2 (Structure of Atom) and Class 12 Chapter 8 (d-block elements) cover electron configuration in detail — both JEE Mains and Advanced papers have appeared with direct configuration identification questions.
Hund's rule states that for a given subshell, electrons occupy separate orbitals singly before pairing, and all singly occupied orbitals have the same spin. This maximises total spin multiplicity and lowers energy. Example: Carbon (C, Z=6): 1s² 2s² 2p² — the two 2p electrons occupy two separate 2p orbitals (not one orbital with paired spins). Nitrogen (N, Z=7): 1s² 2s² 2p³ — three 2p electrons in three separate orbitals, all same spin (↑↑↑). This gives N 3 unpaired electrons and explains its high bond energy (N≡N = 945 kJ/mol — nitrogen is largely inert at room temperature). Hund's rule is tested alongside Aufbau and Pauli exclusion principle in NCERT Class 11 Chapter 2.
Lanthanides (Ce to Lu, Z=58–71) and actinides (Th to Lr, Z=90–103) fill 4f and 5f orbitals respectively, but many have exceptional configurations due to energy near-degeneracy of 4f/5d and 5f/6d orbitals. Gadolinium (Gd, Z=64): [Xe] 4f⁷ 5d¹ 6s² (not 4f⁸ 6s²) — half-filled 4f subshell extra stability. Cerium (Ce, Z=58): [Xe] 4f¹ 5d¹ 6s² (both 4f and 5d occupied). Thorium (Th, Z=90): [Rn] 6d² 7s² (no 5f electrons!). BARC (Bhabha Atomic Research Centre, Trombay, Mumbai) works with actinides U, Pu, Th for India's three-stage nuclear power programme — thorium-based reactors are central to the Department of Atomic Energy's strategy because India has the world's largest thorium reserves (~25% of global, Monazite sand in Kerala coast, Tamil Nadu).
Paramagnetic: contains unpaired electrons → attracted to magnetic field. Diamagnetic: all electrons paired → repelled by magnetic field. Count unpaired electrons from the electron configuration: Mn²⁺ loses 2 electrons from 4s first, then 3d if needed. Mn²⁺: [Ar] 3d⁵ — 5 unpaired electrons → strongly paramagnetic. Fe²⁺: [Ar] 3d⁶ → 4 unpaired electrons. Fe³⁺: [Ar] 3d⁵ → 5 unpaired electrons (more paramagnetic than Fe²⁺!). Cu²⁺: [Ar] 3d⁹ → 1 unpaired electron. Zn²⁺: [Ar] 3d¹⁰ → 0 unpaired electrons → diamagnetic. Magnetic susceptibility measurements are used at IIT research groups and BARC to characterise transition metal coordination compounds — the [Effective Nuclear Charge Calculator](/effective-nuclear-charge-calculator/) and [Bond Order Calculator](/bond-order-calculator/) complement electron configuration analysis.