Zirconium

Atomic number	40
Atomic mass	91.22 g.mol -1
Electronegativity according to Pauling	1.2
Density	6.49 g.cm-3 at 20°C
Melting point	1852 °C
Boiling point	4400 °C
Vanderwaals radius	0.160 nm
Ionic radius	0.08 nm (+4)
Isotopes	11
Electronic shell	[ Kr ] 4d2 5s2
Energy of first ionisation	669 kJ.mol -1
Energy of second ionisation	1346 kJ.mol -1
Energy of third ionisation	2312 kJ.mol -1
Energy of fourth ionisation	3256 kJ.mol -1
Discovered by	Martin Klaproth in 1789

Zirconium is a very strong, malleable, ductile, lustrous silver-gray metal. Its chemical and physical properties are similar to those of titanium. Zirconium is extremely resistant to heat and corrosion. Zirconium is lighter than steel and its hardness is similar to copper. When it is finely divided, the metal can spontaneously ignite in air, especially at high temperatures. Zirconium powder is black and is regarded as very dangerous fire hazard. Zirconium does not dissolve in acids and alkalis.
Applications 
Zirconium is used in alloys such as zircaloy, which is used in nuclear applications since it does not readily absorb neutrons. Also used in catalytic converters, percussion caps and furnace bricks. Baddeleyite and impure zirconium (zirconia) are used in lab crucibles.
The major end uses of zircon (ZrSiO4) are refractories, ceramic opacification and foundry sands. Zircon is also marketed as a natural gemstone used in jewelry. The metal also has many other uses, among them in photographic flashbulbs and surgical instruments, to make the glass for television, in the removal of residual gases from electronic vacuum tubes, and as a hardening agent in alloys, especially steel. The paper and packaging industries are finding that zirconium compounds make good surface coatings because they have excellent water resistance and strength.