Symbol: Zr
Atomic Number: 40
Atomic Weight: 91.224
Element Classification: Transition Metal
Discovered By: Martin Klaproth
Discovery Date: 1789 (Germany)
Name Origin: The mineral, zircon.

Density (g/cc): 6.506
Melting Point (K): 2125
Boiling Point (K): 4650
Appearance: Gray-white, lustrous, corrosion-resistant metal
Atomic Radius (pm): 160
Atomic Volume (cc/mol): 14.1
Covalent Radius (pm): 145
Ionic Radius: 79 (+4e)
Specific Heat (@20C J/g mol): 0.281
Fusion Heat (kJ/mol): 19.2
Evaporation Heat (kJ/mol): 567
Thermal Conductivity (@25C W/m K):
Debye Temperature (K): 250.00
Pauling Negativity Number: 1.33
First Ionizing Energy (kJ/mol): 659.7
Oxidation States: 4
Electronic Configuration: [Kr] 4d2 5s2
Lattice Structure: Hexagonal (HEX)
Lattice Constant (): 3.230
Lattice C/A Ratio: 1.593

Mineral Hardness [no units]: 5.0
Brinell Hardness [/MN m-2]: 650
Vickers Hardness [/MN m-2]: 903

Note: Pure zirconium is a soft, ductile hexagonal close-packed metal that can deform by mechanical twinning if handled aggressively in sectioning and grinding. As with most refractory metals, grinding and polishing removal rates are low and eliminating all polishing scratches and deformation can be difficult. It may even be possible to form mechanical twins in compression mounting. Zirconium alloys can contain very hard phases that make relief control more difficult. To improve polarized light response, it is common practice to chemically polish specimens after mechanical polishing. Alternatively, attack polishing additions can be made to the final polishing abrasive slurry, or vibratory polishing may be employed.

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