Scandium is the chemical element with symbol Sc and atomic number 21. It is a soft, silvery transition metal in group 3 of the periodic table. Scandium is relatively scarce in concentrated ores and is often discussed alongside yttrium and the rare-earth elements because of similarities in occurrence and chemistry.
Scandium quick facts
| Property | Value |
| Symbol | Sc |
| Atomic number | 21 |
| Relative atomic mass | 44.956 |
| Group | 3 |
| Period | 4 |
| Block | d-block |
| State at 20°C | Solid |
| Density | 2.99 g/cm³ |
| Melting point | 1541°C |
| Boiling point | 2836°C |
| Electron configuration | [Ar] 3d¹ 4s² |
| Dominant oxidation state | +3 |
| CAS number | 7440-20-2 |
| Stable natural isotope | ⁴⁵Sc |
Position and chemistry
Scandium is the first d-block element in period 4. Its electron configuration is [Ar] 3d¹ 4s². The overwhelmingly important oxidation state is +3, giving Sc³⁺ compounds chemistry that often resembles the trivalent rare-earth elements.
See the complete CleverlySmart periodic table for its position among all 118 elements.
Physical and chemical properties
Scandium is a lightweight, relatively soft silvery metal. Fresh metal tarnishes in air as oxide forms on the surface. Finely divided scandium can burn readily. It reacts with acids to form scandium(III) salts and hydrogen and, like several electropositive metals, can react with water under suitable conditions.
Occurrence and production
Scandium is dispersed through many minerals but rarely occurs in rich deposits, which makes extraction expensive. It may be recovered from certain rare-earth minerals, uranium-processing residues, nickel and cobalt laterites, or other industrial streams where it is present in low concentrations.
Important compounds
- Scandium oxide (Sc₂O₃): also called scandia; an important starting material for other scandium compounds.
- Scandium chloride (ScCl₃): used in research and chemical preparation.
- Scandium iodide (ScI₃): used in certain high-intensity metal-halide lamps to improve colour rendering.
- Scandium triflate: a strong Lewis-acid catalyst used in specialised organic chemistry.
Uses of scandium
- Aluminium-scandium alloys: small additions of scandium can refine grain structure and improve strength, weldability and high-temperature performance.
- Aerospace and high-performance equipment: scandium-containing aluminium alloys have been used where low weight and high strength are valuable.
- Sports equipment: specialised bicycle frames and other premium products have used Al-Sc alloys.
- Lighting: scandium iodide can be added to metal-halide lamps to produce a spectrum resembling daylight.
- Research and catalysis: scandium compounds are used in materials science and synthetic chemistry.
Scandium isotopes
Natural scandium consists essentially of one stable isotope, ⁴⁵Sc. Several radioactive scandium isotopes are important in research; some, including scandium-44 and scandium-47, are also studied for medical imaging or radiotherapeutic applications.
For a broader isotope reference, see the CleverlySmart complete isotope table.
Biological role and safety
Scandium has no known essential biological role in humans. Toxicological data are more limited than for common metals, so scandium metal, dust and compounds should be handled using appropriate occupational controls. Fine metal powders may present fire hazards.
Discovery and name
Dmitri Mendeleev predicted an element with scandium-like properties and called it ekaboron. Swedish chemist Lars Fredrik Nilson discovered scandium in 1879 while analysing rare-earth minerals, and Per Teodor Cleve recognised that it matched Mendeleev’s prediction. The name comes from Scandia, Latin for Scandinavia.
Frequently asked questions
Why is scandium expensive?
It is widely dispersed in ores but rarely concentrated enough for simple, high-volume extraction, so separation and purification are costly.
What is scandium mainly used for?
Its best-known uses are specialised aluminium alloys, metal-halide lamps, research and catalysis.
Why scandium is valuable in lightweight alloys
Small additions of scandium can strongly improve aluminium alloys. Scandium promotes a fine grain structure and forms stable Al₃Sc precipitates that increase strength, weldability and resistance to recrystallisation. This is why aluminium–scandium alloys are studied for aerospace structures, high-performance sporting equipment and advanced additive manufacturing.
Scandium oxide and advanced ceramics
Scandium oxide (Sc₂O₃) is used in specialist ceramics and high-intensity lighting. Scandia-stabilised zirconia can conduct oxide ions efficiently at high temperature, making it important in research on solid-oxide fuel cells and oxygen sensors.
Scandium is not especially rare in average crustal abundance, but it is highly dispersed and seldom forms rich ores. Commercial supply therefore often comes as a by-product of processing other metals or industrial residues.
Frequently asked questions
Is scandium a rare-earth element?
It is commonly grouped with the rare-earth elements because of its chemistry and occurrence, although it is not a lanthanide.
Why is scandium expensive?
Demand is specialised and production is small because scandium is dispersed through many ores rather than concentrated in easily mined deposits.
