Chemistry

An Overview about the Chemical Element Ytterbium



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Ytterbium

Symbol: Yb

Atomic Number: 70

Atomic Mass: 173.04 amu (atomic mass units)

Melting Point: 819 C (1092 K, 1506 F)

Boiling Point: 1196.0 C (1469 K, 2185 F)

Number of Protons: 70

Number of Electrons: 70

Number of Neutrons: 103

Classification: Rare Earth Metal

Group Name: Lanthanide or Lanthanoid

Crystal Structure: Cubic

Density @ 293 K: 6.90 grams per cubic centimeter

Color: Silver

Many of the rare earth elements are chemically very similar. This has made their original separation from mineral ores and subsequent identification very difficult. The isolation of the element ytterbium shown how complicated and drawn out the process could be.

In 1843 the Swedish chemist Carl Gustaf Mosander separated three substances from the mineral gadolinite. He called these substances erbia, terbia and yttria. A later confusion led to erbia being called terbia and terbia being called erbia. Eventually he found two rare earth elements which were named erbium and terbium.

The Swiss chemist in 1878 Jean Charles Galissard de Marignac separated erbia (formerly known as terbia) into two substances. One kept the name erbia as it contained erbium oxide the other he named ytterbia. He believed that ytterbia contained an element called ytterbium. Over the next few years several scientists attempted to extract this element from ytterbia. Experiments on the products of these extractions were inconclusive and often contradictory.

The next scientist to take part in the search for the new element was the French chemist Georges Urbain who believed yttria might contain not one but two rare earth elements. In 1907 he produced samples containing these two elements which he called neoytterbium and lutecium. Scientists later changed the name of neoytterbium back to ytterbium and lutecium became lutetium.

At the same time as Georges Urbain announced his discovery of ytterbium and lutetium the German scientist Carl Auer Von Welsbach announced the discovery of two new elements that he called "aldebaranium" and "cassiopeium". Von Welsbach's elements were identical to those found by Urbain. Georges Urbain is credited with the discovery of ytterbium and lutetium.

The element's name comes from the village of Ytterby in Sweden. It was in a quarry near this village that the mineral gadolinite was found. Erbium and terbium were also named after this village as was the transitional metal element yttrium.

Pure metal ytterbium is soft, malleable and ductile. A fairly stable element pure ytterbium should still be kept in closed containers to prevent it reacting with water vapor and air. The metal reacts slowly with water. It can be dissolved in mineral acids. The oxidation states of ytterbium are +2 or +3 and its ionization energy is 6.254 eV.

Ytterbium has seven naturally occurring isotopes. In order of natural abundance these isotopes are: ytterbium-174 (31.83%), ytterbium-173 (21.83%), ytterbium-173 (16.13%), ytterbium-171 (14.28%), ytterbium-176 (12.76%), ytterbium-170 (3.04%) and ytterbium-169 (0.13%). Ytterbium-176 an unstable beta emitter with a half-life of greater than 160,000,000,000,000,000 years all the others are stable. Several unstable isotopes have been discovered with mass numbers in the range of 148 to 181. One of these unstable isotopes is being investigated as an X-ray source for portable X-ray machines.

Ytterbium is extracted commercially by the ion exchange process from monazite sand. Monazite sand contains a number of rare earth elements and the radioactive element thorium. The presence of thorium means that radiation safety procedures must be observed during the extraction of the rare earth elements.

A few limited uses for ytterbium have been identified. Alloyed with stainless steel it can improve the metals mechanical properties. It is also used to dope optic fiber cables as it can act as a signal amplifier.

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