Scandium Electron Configuration

Interactive reference for scandium's electron configuration (1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹ 4s²), orbital diagram, quantum numbers, and key atomic properties.

Z = 21 Sc Scandium

Scandium — Electron Configuration

Atomic number 21 · First transition metal · Period 4, Group 3 · d-block

1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹ 4s² [Ar] 3d¹ 4s² 21 electrons 3 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 (first d electron) 1 10 3d¹
4s s orbital, shell n=4 (valence) 2 2 4s²
Total 21

Full Configuration

1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹ 4s²

All subshells written explicitly. Total: 21 electrons.

Noble-Gas Shorthand

[Ar] 3d¹ 4s²

[Ar] = 1s² 2s² 2p⁶ 3s² 3p⁶ (the filled argon core, Z=18).

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 3d¹ 9 / 18 electrons (50%)
Shell 4 (n=4) — 4s² 2 / 32 electrons (6%)

Shell 3 can hold up to 18 electrons (3s + 3p + 3d). Scandium uses 9: the 3d subshell has only 1 electron, making it the very first d-block element. The 4s fills before 3d in Aufbau order, so 4s² appears in the ground state alongside 3d¹.

Scandium as the First Transition Metal

With Z=21, scandium is the first element to place an electron into the 3d subshell. Its single 3d¹ electron alongside the filled 4s² makes it the opening member of the first d-block transition series (Sc through Zn). When scandium reacts, it typically loses all three outer electrons (4s² and 3d¹) to form Sc³⁺, reaching the stable [Ar] configuration — a much lower energy state.

Summary

Interactive reference for scandium's electron configuration (1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹ 4s²), orbital diagram, quantum numbers, and key atomic properties.

How it works

  1. The Aufbau principle fills orbitals from lowest to highest energy.
  2. Scandium's 21 electrons fill through 1s, 2s, 2p, 3s, 3p, 4s, then 3d.
  3. 4s fills before 3d in the ground-state configuration because 4s is lower in energy for lighter elements.
  4. The single 3d¹ electron marks scandium as the first transition metal in Period 4.
  5. Noble-gas notation replaces the argon core (1s² 2s² 2p⁶ 3s² 3p⁶) with [Ar]: [Ar] 3d¹ 4s².
  6. The tabs below let you explore the subshell table, orbital box diagram, and element data.

Use cases

  • Quick reference for chemistry homework or periodic-table exam review.
  • Understand why scandium is classified as a d-block transition metal despite minimal d-electron count.
  • Compare how 3d filling begins with scandium and progresses across the first transition series.
  • Verify quantum numbers for each of scandium's 21 electrons.
  • Teaching aid for introductory atomic structure and electron configuration lessons.
  • Study noble-gas shorthand notation and the concept of core electrons.
  • Understand why scandium commonly forms Sc³⁺ by losing its two 4s and one 3d electron.

Frequently Asked Questions

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