Scandium (Sc): Properties, Reactions, and Uses - Exam Guide

Scandium (Sc), a silvery-white metallic element, is the first transition metal in the periodic table. Despite its relative abundance in the Earth’s crust (comparable to lead), it is rarely found in concentrated deposits, making it challenging to extract and thus expensive. Its unique properties, particularly its low density and high melting point, confer significant advantages in specialized applications.

CBSE/JEE Quick Revision Notes

Symbol: Sc
Atomic Number: 21
Atomic Mass: 44.956 g/mol
Group: 3
Period: 4
Block: d-block (Transition Element)
Nature: Metallic, Silvery-white, Soft
Common Oxidation State: +3 (Exhibits only one stable oxidation state in its compounds, characteristic of the first element in Group 3).
Melting Point: 1541 °C (1814 K)
Density: 2.985 g/cm³
Classification: Often associated with rare earth elements due to similar chemical properties with lanthanides.

Electron Configuration & Bonding Behavior

Ground State Electron Configuration: [Ar] 3d¹ 4s²
Valence Electrons: 3 (one 3d and two 4s electrons).
Ionization: Scandium readily loses all three valence electrons (one 3d electron and two 4s electrons) to achieve a stable noble gas configuration (Argon configuration).
Common Oxidation State: The predominant and almost exclusive oxidation state is +3. This is because the energy required to remove the third electron (from the 3d orbital) is relatively low, leading to a stable Sc³⁺ ion.
Bonding: Primarily forms ionic compounds due to the high electropositivity of Sc³⁺. Covalent character may be observed in some compounds with highly electronegative elements.
Magnetic Properties: Sc³⁺ ion has an [Ar] configuration (0 unpaired electrons), rendering it diamagnetic. Elemental scandium is paramagnetic due to the presence of one unpaired 3d electron.

Crucial Chemical Reactions

Scandium is a reactive metal, though less reactive than alkali and alkaline earth metals.

Reaction with Air/Oxygen

Scandium tarnishes in air and burns readily at elevated temperatures to form scandium(III) oxide.

4Sc(s) + 3O₂(g) → 2Sc₂O₃(s)

Reaction with Acids

Scandium reacts with most dilute acids to form scandium(III) salts and hydrogen gas.

2Sc(s) + 6HCl(aq) → 2ScCl₃(aq) + 3H₂(g) 2Sc(s) + 3H₂SO₄(aq) → Sc₂(SO₄)₃(aq) + 3H₂(g)

Reaction with Halogens

Scandium reacts vigorously with halogens to form scandium(III) halides.

2Sc(s) + 3F₂(g) → 2ScF₃(s) 2Sc(s) + 3Cl₂(g) → 2ScCl₃(s)

Reaction with Water

Scandium reacts slowly with cold water and more rapidly with steam to form scandium(III) hydroxide and hydrogen gas.

2Sc(s) + 6H₂O(l) → 2Sc(OH)₃(s) + 3H₂(g) (slow reaction with cold water)

Formation of Scandium Hydride

Scandium reacts with hydrogen at high temperatures to form a non-stoichiometric hydride.

2Sc(s) + xH₂(g) → 2ScHₓ(s) (where x ≈ 1.5-2)

Industrial and Biological Importance

Industrial Importance

Aerospace Alloys: Scandium is primarily utilized in lightweight, high-strength scandium-aluminum alloys. These alloys are crucial in the aerospace industry for aircraft components, missile parts, and high-performance sporting goods due to their superior strength-to-weight ratio and enhanced ductility.
High-Intensity Discharge Lamps: Scandium iodide is incorporated into mercury vapor lamps to produce high-efficiency, sunlight-like illumination, particularly in stadium and studio lighting.
Solid Oxide Fuel Cells (SOFCs): Scandium-stabilized zirconia (ScSZ) serves as a high-performance electrolyte material for SOFCs due to its superior ionic conductivity compared to yttria-stabilized zirconia.
Tracer in Oil Refining: The radioactive isotope Scandium-46 (⁴⁶Sc) is employed as a tracer in oil refineries to monitor the flow of petroleum products.
Research Applications: Scandium finds use in various research applications, including the production of specialized lasers and in certain superconducting materials.

Biological Importance

Scandium has no known essential biological role in humans or other organisms.
It is generally considered non-toxic in its elemental and common ionic forms, although extensive studies on its biological effects are limited due to its rarity and low exposure.
Trace amounts may be found in plants and animals but are not metabolically active.