40
Zr
Zirconium
91.224
Zirconium (Zr)
Transition MetalGroup 4Period 5d-block-block
Zirconium is a chemical element with symbol Zr and atomic number 40. The name of zirconium is taken from the name of the mineral zircon, the most important source of zirconium. The word zircon comes from the Persian word zargun زرگون, meaning "gold-colored".
Latin name: Zirconium
Atomic Number
40
Atomic Mass
91.224 g/mol
Phase (STP)
Solid
Electron Config.
[Kr] 4d² 5s²
General
SymbolZr
Atomic Number40
Atomic Mass91.224 g/mol
CategoryTransition Metal
Group4
Period5
Blockd-block
Electron Configuration[Kr] 4d² 5s²
Valence Electrons4
Colourgrayish-white metallic
Appearancesilvery white
CAS NumberCAS7440-67-7
Physical Properties
Phase (STP)Solid
Density6.52 g/cm³
Melting Point1854.85°C · 3370.73°F · 2128.00 K
Boiling Point4408.85°C · 7967.93°F · 4682.00 K
Atomic Properties
Atomic Radius206 pm
Electronegativity1.33 Pauling
Ionization Energy640 kJ/mol
Oxidation States+4
Ion ChargeZr4+
Thermodynamic
Molar Heat25.36 J/(mol·K)
Crystal Structure
Crystal Structurehexagonal close-packed
Mechanical Properties
Mohs Hardness5
Abundance
In Earth's Crust0.0165%
Discovery & History
Discovery Year1789
Discovered ByMartin Heinrich Klaproth
Country of DiscoveryGermany
Isotopes of Zirconium
| Isotope | Abundance | Half-life | Decay |
|---|---|---|---|
| Zr-90 | 51.45% | Stable | — |
| Zr-91 | 11.22% | Stable | — |
| Zr-92 | 17.15% | Stable | — |
| Zr-93 | — | 1.53 × 10⁶ years | β⁻ |
| Zr-94 | 17.38% | Stable | — |
| Zr-96 | 2.8% | 2.0 × 10¹⁹ years | β⁻β⁻ |