Zirconium

Today I´m going to talk about zirconium

Zirconium is a greyish-white lustrous metal. The finely divided metal can ignite spontaneously in air, especially at elevated temperatures. The solid metal is much more difficult to ignite. The inherent toxicity of zirconium compounds is low. Hafnium is invariably found in zirconium ores, and the separation is difficult. Commercial grade zirconium contains from 1 to 3% hafnium. The hafnium is removed from the zirconium used in the nuclear power industry.

Zirconium is found in S-type stars, and has been identified in the sun and meteorites. Analyses of lunar rock samples show a surprisingly high zirconium oxide content as compared with terrestrial rocks. Some forms of zircon (ZrSiO₄) have excellent gemstone qualities.

Table: basic information about and classifications of zirconium.

Name: Zirconium Symbol: Zr Atomic number: 40 Atomic weight: 91.224 (2) Standard state: solid at 298 K CAS Registry ID: 7440-67-7

Group in periodic table: 4 Group name: (none) Period in periodic table: 5 Block in periodic table: d-block Colour: silvery white Classification: Metallic

 Small and large samples of zirconium foil like this, as well as sheet and wire, can be purchased from Advent Research Materials via their web catalogue.

Zirconium: historical information

Zirconium was discovered by Martin Heinrich Klaproth at 1789 in Berlin, Germany. Origin of name: from the Arabic word "zargun" meaning "gold colour".

                                  

 

 

 

 

 

 

The name zircon probably originated from the arabic "zargun", which describes the colour of the gemstone now known as zircon (ZrSiO₄). The minerals jargon, hyacinth, and jacinth also contain zircon and these have been known since biblical times and are mentioned in the bible in several places. The existence of a new element within these minerals was not suspected until studies by Martin Heinrich Klaproth in the late 18th century.

The impure metal was first isolated by Jöns Jacob Berzelius in 1824 who heated a mixture of potassium and potassium zirconium fluoride together in an iron tube. Pure zirconium was first prepared in 1914.

Zirconium: physical properties

• Melting point: 2128 [or 1855 °C (3371 °F)]
• Boiling point: 4682 [or 4409 °C (7968 °F)] K
• Density of solid: 6511 kg m^-3

 

Zirconium: orbital properties

• Ground state electron configuration:  [Kr].4d².5s²
• Shell structure:  2.8.18.10.2
• Term symbol:   ³F₂
• Pauling electronegativity: 1.33 (Pauling units)
•  First ionisation energy: 640.1 kJ mol^-1
•  Second ionisation energy:  1270 kJ mol^-1

 

Isolation

Isolation: zirconium is available from commercial sources so preparation in the laboratory is not normally required. In industry, reduction of ores with carbon is not a useful option as intractable carbides are produced. As for titanium, the Kroll method is used for zirconium and involves the action of chlorine and carbon upon baddeleyite (ZrO₂). The resultant zirconium tetrachloride, ZrCl₄, is separated from the iron trichloride, FeCl₃, by fractional distillation. Finally ZrCl₄ is reduced to metallic zirconium by reduction with magnesium, Mg. Air is excluded so as to prevent contamination of the product with oxygen or nitrogen.

ZrO₂ + 2Cl₂ + 2C (900°C) → ZrCl₄ + 2CO

ZrCl₄ + 2Mg (1100°C) → 2MgCl₂ + Zr

Excess magensium and magnesium dichloride is removed from the product by treatment with water and hydrochloric acid to leave a zirconium "sponge". This can be melted under helium by electrical heating.