Zirconium
Element 40 · Transition Metal
Zirconium is a lustrous gray-white metal prized for two opposite talents: it shrugs off corrosion from acids and seawater, and it barely absorbs neutrons, which makes it the ideal cladding for uranium fuel rods in nuclear reactors. It is also the backbone of advanced ceramics — zirconium dioxide (zirconia) is extraordinarily hard and heat-resistant, serving as thermal-barrier coatings, dental crowns, and the lab-grown gemstone cubic zirconia. Zirconium is chemically similar to titanium and hafnium, and separating it from hafnium is one of the trickier tasks in metallurgy.
Key facts
| Atomic number | 40 |
|---|---|
| Atomic weight | 91.224 |
| Category | Transition Metal |
| Group / Period | 4 / 5 |
| Block | d |
| Electron configuration | [Kr] 4d2 5s2 |
| Common oxidation states | +4, +3 |
| State at STP | Solid |
| Electronegativity | 1.33 |
| Atomic radius | 155 pm (empirical) |
| Density | 6.52 g/cm³ |
| Melting point | 1855 °C |
| Boiling point | 4409 °C |
Occurrence
Zirconium is the 18th most abundant element in Earth's crust. It is mined mainly from the mineral zircon (zirconium silicate), concentrated in heavy beach sands, and from baddeleyite.
Applications
Nuclear fuel cladding (zircaloy)
Heat-resistant ceramics and refractories
Cubic zirconia gemstones
Dental crowns and implants
Common compounds
- Zirconium dioxide
- Zircon (zirconium silicate)
- Zirconium tetrachloride
Cubic zirconia, the lab-grown crystal of zirconium dioxide, is the most popular diamond imitation in jewelry — chemically it is simply a tough ceramic.
Data source: IUPAC standard atomic weights 2021; NIST physical property data