Scandium
Atomic Data
| Atomic Number | 21 |
| Symbol | Sc |
| Atomic Weight | 44.956 u |
| Density (STP) | 2.985 g/cm³ |
| Melting Point | 1540.85 °C (1814 K) |
| Boiling Point | 2835.85 °C (3109 K) |
| Electronegativity | 1.36 (Pauling) |
| Electron Config. | 1s2 2s2 2p6 3s2 3p6 3d1 4s2 |
| Oxidation States | +3 |
| Phase at STP | Solid |
| Category | Transition Metal |
| Period / Group | 4 / 3 |
| CAS Number | 7440-20-2 |
Electron Configuration
[Ar] 3d1 4s2
| Shell | n | Subshell | Electrons | Cumulative |
|---|---|---|---|---|
| K | 1 | 1s | 2 | 2 |
| L | 2 | 2s | 2 | 4 |
| L | 2 | 2p | 6 | 10 |
| M | 3 | 3s | 2 | 12 |
| M | 3 | 3p | 6 | 18 |
| M | 3 | 3d | 1 | 19 |
| N | 4 | 4s | 2 | 21 |
| Total | 21 | 21 | ||
Isotopes of Scandium
Scandium is monoisotopic — ⁴⁵Sc is its only naturally occurring stable isotope, accounting for 100% of all natural Scandium.
| Isotope | Symbol | Protons | Neutrons | Abundance | Stability |
|---|---|---|---|---|---|
| Scandium-45 | ⁴⁵Sc | 21 | 24 | 100 | Stable |
Abundance & Occurrence
Scandium is present in Earth's crust at approximately 22 ppm by mass and at approximately 3 ppm by mass throughout the universe.
Earth's Crust (ppm by mass)
Universe (ppm by mass)
Discovery & History
Read more about the discovery of the periodic table of elements →
Safety & Handling
- Dust inhalation: Scandium metal dust and oxide are respiratory irritants; as with other rare-earth metals, fine particles should not be inhaled — use respiratory protection when machining or grinding.
- Fire hazard: Scandium powder is flammable and can ignite in air; metal fires require Class D extinguishing agents — water must not be used on burning metal powders.
- Limited toxicity data: Scandium has low acute toxicity by oral and dermal routes; its long-term biological effects are not well characterised, so general metal handling precautions apply.
- Storage: Store in sealed containers under inert gas or dry conditions; avoid contact with strong oxidising agents or halogenated compounds.
Scandium in the Real World
Real-World Uses
- Aluminium-scandium alloys — Adding 0.1–0.5% scandium to aluminium alloys dramatically refines the grain structure, increasing strength, weld quality, and resistance to stress corrosion; used in high-performance bicycle frames, baseball bats, and aerospace components.
- Solid oxide fuel cells — Scandium-stabilised zirconia (ScSZ) is a high-performance electrolyte for solid oxide fuel cells (SOFCs) that operate at lower temperatures than yttrium-stabilised alternatives, improving efficiency and durability.
- Metal halide lamps — Scandium iodide added to mercury metal halide lamps produces a high colour rendering index and high luminous efficacy output used in stadium floodlights, film and television studio lighting, and colour-critical retail lighting.
- Defence and sporting equipment — Sc-Al alloys are used in the receiver and barrel of lightweight military rifles and in lacrosse stick shafts; the Russian MiG-29 aircraft incorporated scandium alloys to reduce weight.
Downloadable Resources
Free periodic table reference sheets for classrooms, study sessions, and laboratory use.
Frequently Asked Questions
What is scandium used for?
Scandium is used primarily as an alloying agent in aerospace-grade aluminium alloys, where small additions dramatically increase strength while keeping weight low. It is also used in solid oxide fuel cells and in high-intensity metal halide lamps that produce a light closely matching natural sunlight.
Is scandium rare?
Yes. Scandium is considered a rare element because, despite being relatively abundant in Earth's crust at around 22 parts per million, it is widely dispersed and rarely concentrated into ore deposits large enough to mine economically. Most commercial scandium is recovered as a byproduct of uranium and titanium processing.
How was scandium discovered?
Scandium was discovered in 1879 by Swedish chemist Lars Fredrik Nilson, who isolated it from the mineral euxenite. It matched the properties Dmitri Mendeleev had predicted for 'eka-boron' in his 1869 periodic table, a striking early validation of the periodic law.
Why is scandium important to materials science?
Adding just 0.1–0.5% scandium to aluminium produces an alloy with grain refinement and age-hardening properties comparable to much heavier metals. This makes scandium-aluminium alloys attractive for aircraft frames, bicycle frames, and high-performance sports equipment where every gram matters.