Erbium (68)

It has recently been brought to my attention (read, TODAY) that i left out an element of the Lanthanide series. Ladies and gentlemen, I give you:

ERBIUM

Pure erbium metal is soft and malleable and has a bright, silvery, metallic luster. As with other rare-earth metals, its properties depend to a certain extent on impurities present. The metal is fairly stable in air and does not oxidize as rapidly as some of the other rare-earth metals.

Erbium

Symbol: Er

Atomic number: 68

Atomic weight: 167.259 (3) [see note g]

Standard state: solid at 298 K

CAS Registry ID: 7440-52-0

Group name: Lanthanoid

Period in periodic table: 6 (lanthanoid)

Block in periodic table: f-block

Color: silvery white

Classification: Metallic

Historical information

Erbium was discovered by Carl G. Mosander at 1842 in Sweden. Origin of name: named after the village of "Ytterby" near Vaxholm in Sweden. 

(this section gets a bit confusing...)

In 1842 Gustav Mosander separated "yttria", found in the mineral gadolinite, into three fractions which he called yttria, erbia, and terbia. The names erbia and terbia became confused in this early period. After 1860, Mosander's terbia was known as erbia, and after 1877, the earlier known erbia became terbia. The erbia of this period was later shown to consist of five oxides, now known as erbia, scandia, holmia, thulia and ytterbia. Klemm and Bommer first produced reasonably pure erbium metal in 1934 by reducing the anhydrous chloride with potassium vapour.

Physical properties

Melting point: 1802 [or 1529 °C (2784 °F)] K

Boiling point: 3141 [or 2868 °C (5194 °F)] K

Density of solid: 9066 kg m-3

Orbital properties

Ground state electron configuration:  [Xe].4f12.6s2

Shell structure:  2.8.18.30.8.2

Isolation

Erbium metal is available commercially so it is not normally necessary to make it in the laboratory, which is just as well as it is difficult to isolate as the pure metal. This is largely because of the way it is found in nature. The lanthanoids are found in nature in a number of minerals. The most important are xenotime, monazite, and bastnaesite. The first two are orthophosphate minerals LnPO4 (Ln deonotes a mixture of all the lanthanoids except promethium which is vanishingly rare) and the third is a fluoride carbonate LnCO3F. Lanthanoids with even atomic numbers are more common. The most comon lanthanoids in these minerals are, in order, cerium, lanthanum, neodymium, and praseodymium. Monazite also contains thorium and ytrrium which makes handling difficult since thorium and its decomposition products are radioactive.

For many purposes it is not particularly necessary to separate the metals, but if separation into individual metals is required, the process is complex. Initially, the metals are extracted as salts from the ores by extraction with sulphuric acid (H2SO4), hydrochloric acid (HCl), and sodium hydroxide (NaOH). Modern purification techniques for these lanthanoid salt mixtures are ingenious and involve selective complexation techniques, solvent extractions, and ion exchange chromatography.

Pure erbium is available through the reduction of ErF3 with calcium metal.

2ErF3 + 3Ca → 2Er + 3CaF2

This would work for the other calcium halides as well but the product CaF2 is easier to handle under the reaction conditions (heat to 50°C above the melting point of the element in an argon atmosphere). Excess calcium is removed from the reaction mixture under vacuum.