Electron Configuration
Find the electron configuration, noble gas shorthand, and valence electrons for any element from hydrogen to oganesson. Free online chemistry calculator with orbital filling charts and shell breakdowns.
About This Calculator
Our Electron Configuration Calculator helps chemistry students, teachers, and professionals quickly find the complete electron configuration of any element from hydrogen (Z=1) to oganesson (Z=118). Simply select an element from the dropdown to instantly view its full electron configuration, noble gas shorthand notation, valence electron count, and atomic mass.
Electron configuration follows three key principles: the Aufbau principle (electrons fill orbitals in order of increasing energy), the Pauli exclusion principle (each orbital holds at most two electrons with opposite spins), and Hund's rule (electrons fill degenerate orbitals singly before pairing). The filling order is 1s → 2s → 2p → 3s → 3p → 4s → 3d → 4p → 5s → 4d → 5p → 6s → 4f → 5d → 6p → 7s → 5f → 6d → 7p, following the n+l rule.
This tool also handles well-known exceptions to the standard filling order, including chromium ([Ar]3d⁵4s¹) and copper ([Ar]3d¹⁰4s¹), where a half-filled or completely filled d-subshell provides extra stability. The orbital distribution chart and shell breakdown table (K, L, M, N, O shells) help visualize how electrons are arranged around the nucleus.
Electron configuration is fundamental to understanding chemical bonding, periodic trends, and the physical properties of elements. The valence electrons shown by this calculator determine an element's reactivity and chemical behavior. For example, elements in group 1 have one valence electron and are highly reactive, while noble gases have full outer shells (8 valence electrons for most) and are chemically inert.
Frequently Asked Questions
What is electron configuration?
Electron configuration describes the distribution of electrons among the orbital shells and subshells of an atom in its ground state. Electrons occupy orbitals in order of increasing energy following the Aufbau principle, with each orbital holding a maximum of two electrons with opposite spins according to the Pauli exclusion principle.
How do I write electron configuration using the shorthand method?
To write shorthand electron configuration, first find the noble gas that comes before the element in the periodic table. Put its symbol in square brackets, then write only the remaining orbitals. For example, carbon (C) has full configuration 1s²2s²2p², and its shorthand is [He]2s²2p² since helium is the preceding noble gas.
What are valence electrons?
Valence electrons are the electrons in the outermost shell or subshell of an atom. They determine the chemical properties of an element and are involved in bond formation. For main-group elements, the number of valence electrons equals the group number (for groups 1-2) or group number minus 10 (for groups 13-18).
Why do chromium and copper have unusual electron configurations?
Chromium (Z=24) and copper (Z=29) are exceptions to the standard filling order because a half-filled (d⁵) or completely filled (d¹⁰) d-subshell provides extra stability. Chromium has [Ar]3d⁵4s¹ instead of [Ar]3d⁴4s², and copper has [Ar]3d¹⁰4s¹ instead of [Ar]3d⁹4s².
How many electrons can each orbital subshell hold?
The s subshell holds up to 2 electrons, p holds up to 6, d holds up to 10, and f holds up to 14 electrons. The total electrons per shell are: K shell (n=1) holds 2, L shell (n=2) holds 8, M shell (n=3) holds 18, N shell (n=4) holds 32, and so on following 2n².
How can I find the electron configuration of an ion?
For a cation (positive ion), remove electrons from the outermost subshell first. For example, Fe²⁺ removes two 4s electrons from [Ar]3d⁶4s² to give [Ar]3d⁶. For an anion (negative ion), add electrons to the outermost subshell. For example, Cl⁻ adds one electron to [Ne]3s²3p⁵ to give [Ne]3s²3p⁶.
What is the electron configuration of oxygen?
Oxygen (Z=8) has the electron configuration 1s²2s²2p⁴. In shorthand notation, this is written as [He]2s²2p⁴. Oxygen has 6 valence electrons (2 in the 2s subshell and 4 in the 2p subshell), which places it in group 16 of the periodic table.
What is the order of filling orbitals according to the Aufbau principle?
The order of orbital filling is: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p. This follows the n + l rule where orbitals are filled in order of increasing (n + l), and for equal (n + l), lower n fills first.