Zirconium, Physical and Chemical Properties

Physical Properties

Zirconium is a refractory metal with a high melting point. Its chief mineral is zircon, ZrSiO₄, which always contains about 1% hafnium – another refractory metal with a high melting point. Both zirconium and hafnium are transition metals, i.e., they are less reactive than the typical metals but more reactive than the less typical metals. The transition metals are characterized by having the outermost electron shell containing two electrons and the next inner shell an increasing number of electrons. Although zirconium [and hafnium] has two electrons in the outermost shell and it would have been expected that to have valency of 2, yet its valency is 4.

Atomic number	40
Atomic weight	91.224
Relative abundance in Earth’s crust, %	2.2×10−2
Atomic radius, nm	15.90
Ionic radius (Zr4+), nm	7.5
Standard potential M/MO2, V	1.53
Melting point, °C	1,852 ± 2
Boiling point, °C	3,850
Crystal structure
ω-Zr	Hexagonal open
α-Zr	Hexagonal dense
	a = 32.3 mm
	c = 51.5 nm
β-Zr	Body-center...