🎓 Chemistry • Atomic Chemistry
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Electron Configuration Tool
Displays full orbital occupancy (1s² 2s² 2p⁶...) and noble gas core shorthand with valence electron counts for chemical elements.
Select Chemical Element
Computes ground state Aufbau orbital configurations & subshell filling.
Popular:
Noble Gas Core Configuration
[Ar] 4s² 3d⁶
Element: Iron (Fe) | Atomic Number Z = 26
Full Aufbau Spectroscopic Sequence:
1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d⁶
Valence Electrons
2
Periodic Block
d-block
Period & Group
Period 4, Grp 8
Total Electrons
26 e⁻
Concentric Bohr Energy Shells (K, L, M, N, O, P, Q)
What is Electron Configuration?
Electron configuration describes the distribution of electrons of an atom across atomic orbitals according to the Aufbau principle, Pauli exclusion principle, and Hund’s rule.
Formula & Step-by-Step Calculation
Aufbau Order: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p...
Orbitals fill in order of increasing energy (n + l rule).
Worked Step-by-Step Examples
Example 1
Electron configuration of Iron (Fe, Z = 26)
Solution: [Ar] 3d⁶ 4s² (Full: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁶ 4s²)
• Argon core (18e) + 4s² (2e) + 3d⁶ (6e) = 26 electrons
Common Real-World & Academic Use Cases
- ✓ Predicting chemical bonding and valency
- ✓ Transition metal coordination complex magnetism
- ✓ Periodic table trends (atomic radius, electronegativity)
How to Use the Electron Configuration Tool
1
Select Element
Choose element by atomic number Z or symbol.
2
View Configuration
Inspect full Aufbau notation, noble gas core, and valence electrons.
Frequently Asked Questions
Q: Why does Chromium fill 3d⁵ 4s¹ instead of 3d⁴ 4s²?
Half-filled and fully-filled d subshells possess enhanced exchange energy stability.