Scandium Element Properties
Complete reference for Scandium (Sc, element 21): atomic data, electron configuration, isotopes, physical constants, and unit converter.
Scandium
Transition Metal — Period 4, Group 3
Atomic Identity
Periodic Table Locator — Period 4 Neighborhood
Scandium (Z=21) is the first d-block transition metal in Period 4, sitting between calcium (alkaline earth metal) and titanium. It is directly above yttrium (Z=39) in Group 3 and is sometimes grouped with the rare earth elements in industry despite not being a lanthanide.
Electron Configuration
One unpaired 3d electron — weakly attracted to magnetic fields
Key Isotopes of Scandium
| Isotope | Symbol | Protons | Neutrons | Mass (u) | Natural Abundance | Stability |
|---|---|---|---|---|---|---|
| Scandium-44 | ⁴⁴Sc | 21 | 23 | 43.9594010 | Radioactive |
Unstable
β⁺/EC decay, t½ = 3.97 h |
| Scandium-45 | ⁴⁵Sc | 21 | 24 | 44.9559119 | 100% | Stable |
| Scandium-46 | ⁴⁶Sc | 21 | 25 | 45.9551719 | Radioactive |
Unstable
β⁻ decay, t½ = 83.79 d |
| Scandium-47 | ⁴⁷Sc | 21 | 26 | 46.9524075 | Radioactive |
Unstable
β⁻ decay, t½ = 3.349 d |
| Scandium-48 | ⁴⁸Sc | 21 | 27 | 47.9522236 | Radioactive |
Unstable
β⁻ decay, t½ = 43.67 h |
Scandium is monoisotopic — all naturally occurring scandium is Sc-45. Sc-46 (t½ = 83.79 d) is the most commercially important radioisotope, used as a radioactive tracer in oil refinery cracking processes and hydrology. Sc-44 and Sc-47 are investigated for targeted radionuclide therapy in oncology.
Physical Properties
Chemical Properties
Ground State Quantum Numbers
Notable Emission Lines
Scandium has a rich emission spectrum used in metal halide arc lamps, producing light with a spectral distribution close to sunlight (CRI > 90). The 391 nm line is used in atomic absorption spectroscopy for scandium quantification.
Property Unit Converter
Convert common Scandium property values between units. Enter a value and select the conversion.
Common Scandium Compounds
| Compound | Formula | Common Name | Key Uses |
|---|---|---|---|
| Scandium oxide | Sc₂O₃ | Scandia | High-temperature ceramics, electronic substrates, stabilized zirconia dopant, optical coatings |
| Scandium chloride | ScCl₃ | Scandium trichloride | Synthesis intermediate; Lewis acid catalyst precursor; starting material for metalorganic Sc chemistry |
| Scandium triflate | Sc(OTf)₃ | Scandium(III) triflate | Powerful water-stable Lewis acid catalyst for Diels-Alder, Friedel-Crafts, and aldol reactions in organic synthesis |
| Scandium iodide | ScI₃ | Scandium triiodide | Additive in metal halide arc lamps to produce high-CRI daylight-spectrum lighting |
| Scandium fluoride | ScF₃ | Scandium trifluoride | Negative thermal expansion material; nuclear applications; optical fiber components |
| Scandium nitrate | Sc(NO₃)₃ | Scandium(III) nitrate | Analytical reagent; precursor for sol-gel scandium oxide coatings |
| Scandium carbide | Sc₂C | Scandium carbide | Component in endohedral fullerenes (Sc₂C₂@C₈₄); hard ceramic research |
| Aluminum scandium | Al-Sc alloy | Sc-modified aluminum | Aerospace structural parts, high-performance bicycle frames, lacrosse sticks, baseball bats |
Key Facts About Scandium
First d-block Transition Metal
Scandium (Z=21) is the first element in the d-block, marking the start of the transition metals in Period 4. Its single 3d electron distinguishes it from the s-block alkaline earth metals. Despite this, scandium behaves more like aluminum in its chemistry due to its almost exclusive +3 oxidation state and the small, highly charged Sc³⁺ ion.
Predicted by Mendeleev
Dmitri Mendeleev predicted the existence of scandium in 1871, calling it "ekaboron" and forecasting its atomic mass (~44 u), density (~3.0 g/cm³), and oxide formula (Sc₂O₃). Lars Fredrik Nilson discovered the element in 1879 in the minerals euxenite and gadolinite, and Per Teodor Cleve recognized it as Mendeleev's predicted element — a landmark validation of the periodic law.
Remarkable Alloy Strengthener
Adding just 0.1–0.5% scandium to aluminum creates an alloy with dramatically improved strength, hardness, and resistance to heat and corrosion. Sc pins grain boundaries during welding, preventing the softening that normally occurs in heat-affected zones. The resulting Al-Sc alloys rival titanium in specific strength while being lighter, and are used in MIG-welded aerospace structures, bicycle frames, and sports equipment.
Sunlight-Quality Arc Lamps
Scandium iodide (ScI₃) is the key additive in metal halide arc lamps used in sports stadiums, film studios, and theatrical lighting. The ScI₃ broadens the emission spectrum of mercury arc lamps to closely mimic natural daylight, achieving a color rendering index (CRI) above 90. This application consumes a significant fraction of the world's annual scandium production.
Negative Thermal Expansion in ScF₃
Scandium trifluoride (ScF₃) is one of only a handful of materials that shrinks when heated over a wide temperature range (from near absolute zero to over 1000 K). This unusual negative thermal expansion (NTE) behavior arises from transverse vibrational modes in its rigid ReO₃-type crystal structure. ScF₃ is studied for thermal management composites and precision engineering components where dimensional stability over temperature is critical.
Critical Mineral for Solid Oxide Fuel Cells
Scandium-stabilized zirconia (ScSZ) — typically 9–11 mol% Sc₂O₃ in ZrO₂ — has the highest known ionic conductivity among oxide ion conductors at 700–800 °C, roughly 3–5× higher than the more common yttria-stabilized zirconia (YSZ). ScSZ electrolytes allow solid oxide fuel cells (SOFCs) to operate at lower temperatures, extending stack lifetimes and reducing system costs. This makes scandium a strategically important mineral for clean energy infrastructure.
Summary
Complete reference for Scandium (Sc, element 21): atomic data, electron configuration, isotopes, physical constants, and unit converter.
How it works
- Browse the atomic identity section for symbol, atomic number, and standard atomic weight.
- Check the electron configuration panel for orbital notation and quantum numbers.
- Review the isotopes table for stable and notable radioactive isotopes with natural abundances.
- Consult the physical and chemical properties panels for melting point, density, ionization energies, and more.
- Use the interactive unit converter to convert scandium property values between common units.
- Explore the mini periodic table locator to visualize where scandium sits among neighboring elements.
Use cases
- Look up scandium constants for chemistry homework or exams.
- Verify atomic data when writing lab reports or research papers.
- Reference isotope data for nuclear chemistry or radioisotope tracer research.
- Convert melting and boiling points between Celsius, Fahrenheit, and Kelvin.
- Teach or learn d-block transition metal properties using scandium as an introduction.
- Confirm electron configuration before writing molecular orbital or coordination chemistry problems.
- Research scandium alloys for aerospace or sports equipment material science work.
- Quick-reference ionization energies for electrochemistry or spectroscopy calculations.