Selenium Electron Configuration

Reference for selenium's electron configuration (1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁴), orbital box diagram, quantum numbers, and key atomic properties.

Z = 34 Se Selenium

Selenium — Electron Configuration

Atomic number 34 · Chalcogen · Period 4, Group 16 · p-block

1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁴ [Ar] 3d¹⁰ 4s² 4p⁴ 34 electrons 6 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 4 6 4p⁴
Total 34

Full Configuration

1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁴

All subshells written explicitly.

Noble-Gas Shorthand

[Ar] 3d¹⁰ 4s² 4p⁴

[Ar] = 1s² 2s² 2p⁶ 3s² 3p⁶ (the filled argon 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 4p⁴ 6 / 32 electrons (19%)

Shell 4 can hold up to 32 electrons (4s + 4p + 4d + 4f). Selenium uses 6 of those 32 slots.

Summary

Reference for selenium's electron configuration (1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁴), orbital box diagram, quantum numbers, and key atomic properties.

How it works

  1. The Aufbau principle fills orbitals from lowest to highest energy.
  2. Selenium's 34 electrons fill subshells in order: 1s, 2s, 2p, 3s, 3p, 3d, 4s, then 4p.
  3. The 3d subshell holds 10 electrons across five orbitals, all fully paired.
  4. The 4p subshell holds 4 electrons: two orbitals with paired electrons, one orbital with a single unpaired electron — consistent with Hund's rule.
  5. Noble-gas notation replaces the inner filled shells with argon in brackets: [Ar] 3d¹⁰ 4s² 4p⁴.
  6. Selenium is a chalcogen (Group 16) and behaves similarly to oxygen and sulfur.

Use cases

  • Quick reference for chemistry homework or exam review on d-block and p-block elements.
  • Visualize how the 3d subshell fills before the 4p subshell in Period 4 elements.
  • Understand why selenium commonly forms −2, +2, +4, and +6 oxidation states.
  • Compare selenium to neighboring elements arsenic and bromine in Period 4.
  • Teaching aid for introductory atomic structure and electron configuration lessons.
  • Verify quantum numbers for each of selenium's 34 electrons.
  • Explore how selenium's 4p⁴ configuration makes it similar in chemistry to sulfur.

Frequently Asked Questions

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