Titanium, Zirconium, and Hafnium

Titanium, zirconium, and hafnium belong to the group IVB of the periodic table. A characteristic feature of these transition elements is the ease with which they form stable complex ions. Features that contribute to this ability are favorably high charge-to-radius ratios and the availability of unfilled d orbitals. The ability of forming metallic bonds is demonstrated by the existence of a wide variety of alloys among different transition metals. Other features of these metals are high densities, high melting points, and low vapor pressures. Within this group, these properties tend to increase with increasing atomic weight. This chapter discusses the chemical and physical properties followed by the toxicity of each chemical and compound in three sections: the first section provides details on titanium, the second section on zirconium, and the third section on hafnium. Tables present the atomic number, atomic weight, and natural isotopes of titanium, zirconium, and hafnium. Keywords: Alloys; by-products; exposure assessment; hafnium; hafnium compounds; lung function; physical and chemical properties; production; occurrence; standards, guidelines, and regulations; superalloys; titanium; titanium compounds; toxic effects; use; zirconium; zirconium compounds