Elements

Electron configuration of Scandium (Sc)

Read the Scandium electron configuration, noble-gas shorthand, valence shell, orbital filling logic, and the mistakes to avoid when writing Sc.

Guide: Guía práctica Read: 5 min Updated: 2026-06-27

Element guide

Electron configuration of Scandium (Sc)

The electron configuration of Scandium is 1s2 2s2 2p6 3s2 3p6 3d1 4s2. In shorthand form it is written as [Ar] 3d1 4s2.

Use this page to connect the notation with atomic number 21, the d-block, and the valence pattern 3d1 4s2.

How to write the configuration

Configuration at a glance

Scandium has atomic number 21, so a neutral atom has 21 electrons. The configuration 1s2 2s2 2p6 3s2 3p6 3d1 4s2 is a compact record of where those electrons sit by subshell.

The shorthand [Ar] 3d1 4s2 replaces the filled inner core with the previous noble gas. That notation keeps attention on the electrons that usually explain bonding, ions, and periodic trends.

Scandium as the first transition metal

Scandium is the first element in the d-block of period 4. After filling the argon core (1s2 2s2 2p6 3s2 3p6 = 18 electrons), three electrons remain. According to the Aufbau principle, the 4s subshell fills before 3d, so the order is 4s2 then 3d1.

Step-by-step filling walkthrough: 1. Start with atomic number 21. 2. Follow the Aufbau sequence: fill 1s, 2s, 2p, 3s, 3p, then 4s, finally 3d. 3. Keep a running total: 1s2 (2), 2s2 (4), 2p6 (10), 3s2 (12), 3p6 (18), 4s2 (20), 3d1 (21). 4. Write the noble-gas shorthand by replacing the argon core with [Ar]. 5. Verify: add every superscript and confirm the total equals 21.

Orbital diagram and valence meaning

An orbital diagram turns each subshell into boxes and arrows. Sc has paired electrons up through 4s2, then one unpaired electron in the 3d subshell. The valence clue for Sc is 3d1 4s2.

For transition metals, the valence electrons include both the 4s and 3d electrons. Scandium typically forms Sc3+ by losing all three outer electrons (4s2 and 3d1).

Common mistakes

The first mistake is writing 3d before 4s. In the neutral atom, 4s fills before 3d. However, when writing configurations sorted by principal quantum number, Sc is sometimes written as 1s2 2s2 2p6 3s2 3p6 3d1 4s2. Both ordering conventions are acceptable as long as the superscripts add up to 21.

The second mistake is forgetting that transition-metal ions lose 4s electrons first. Sc3+ has configuration [Ar] with no 4s or 3d electrons remaining.

Scandium reference table

Item Value
Atomic number 21
Full configuration 1s2 2s2 2p6 3s2 3p6 3d1 4s2
Noble-gas notation [Ar] 3d1 4s2
Valence clue 3d1 4s2
Block d-block

Use the table as a learning reference, then verify advanced oxidation-state questions with your course material.

Before you submit an answer

  • The superscripts add up to 21 for a neutral Scandium atom.
  • The notation follows the filling order used in your course.
  • The last occupied subshell matches the periodic-table block.
  • Any transition-metal or actinide exception is checked against a reference.
  • The shorthand core is a noble gas, not a random previous element.

Common questions

What is the electron configuration of Scandium?

The neutral Scandium atom is written as 1s2 2s2 2p6 3s2 3p6 3d1 4s2. The shorthand form is [Ar] 3d1 4s2.

How many valence electrons does Scandium have?

Start from the outer-shell clue 3d1 4s2. For transition metals, inspect both s and d electrons carefully. Scandium has 3 valence electrons.

Should I memorize this configuration?

Memorize the filling pattern first. Individual configurations become easier when you can rebuild them from atomic number, noble-gas cores, and periodic-table position.

What is the configuration of Sc3+?

Sc3+ loses the 4s2 and 3d1 electrons, giving it the configuration [Ar], the same as a neutral argon atom.

Study notes and practice checks

From answer to understanding

Scandium is a critical element for understanding transition metal chemistry. It is the first element where the 3d subshell begins to fill after the 4s subshell. Practice rebuilding [Ar] 3d1 4s2 from scratch: remember that argon accounts for 18 electrons, leaving 3 electrons to place in the 4s and 3d subshells.

Practice comparison

Compare Scandium (Sc) with Calcium (Ca) and Titanium (Ti). Ca: [Ar] 4s2, Sc: [Ar] 3d1 4s2, Ti: [Ar] 3d2 4s2. The pattern shows how d electrons begin filling while keeping 4s2 intact. This progression is the foundation of the first transition series.

Teacher and self-study notes

Scandium is often used in solid oxide fuel cells and aerospace alloys. Despite being the lightest transition metal, its chemistry is dominated by the Sc3+ ion. Use this page as a starting point before exploring later transition metals with d-electron exceptions.

Elena Marquez

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Elena Marquez

Chemistry educator and study-guide editor

Elena explains electron configurations, orbital diagrams, and periodic trends for learners who need clear steps before memorization. Her guides focus on counting, notation, and common classroom mistakes.

Credenciales: Editorial specialization in introductory chemistry, periodic trends, and student reference material.

Experiencia: More than eight years preparing practical chemistry explainers, worksheets, and reference material for independent learners.

Actualizado: 2026-06-27 Politica editorial Correcciones

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