Europium, abundance

Figure 9.9 REE abundances from archaeological glass, showing the effect of chondrite normalization, (a) shows the raw abundances of the REE measured on a set of English medieval window glasses, with the saw-tooth pattern evident, and little indication of differences between any of the samples (apart from perhaps one which has lower overall REE concentrations), (b) shows the same data normalized to the chondrite data (Table 9.1). The saw-tooth has largely disappeared, and close inspection suggests that two samples have a positive europium anomaly, possibly indicating a different geographical origin.

Europium is one of the most rare of the rare-earths. Its abundance on Earth is only 1.1 ppm. It is a soft, shiny, steel-gray metal that is quite ductile and malleable, which means it can be worked and formed into many shapes. It looks like and feels like the element lead (Pb), but is somewhat heavier. It is the most chemically active of all the rare-earths. 

Europium is the 13th most abundant of all the rare-earths and the 55th most abundant element on Earth. More europium exists on Earth than all the gold and silver deposits. Like many other rare-earths, europium is found in deposits of monazite, bastnasite, cerite, and allanite ores located in the river sands of India and Brazil and in the beach sand of Florida. It has proven difficult to separate europium from other rare-earths. Today, the ion-exchange... 

Fig. 5.5. Decomposition of Solar System abundances into r and s processes. Once an isotopic abundance table has been established for the Solar System, the nuclei are then very carefully separated into two groups those produced by the r process and those produced by the s process. Isotope by isotope, the nuclei are sorted into their respective categories. In order to determine the relative contributions of the two processes to solar abundances, the s component is first extracted, being the more easily identified. Indeed, the product of the neutron capture cross-section with the abundance is approximately constant for aU the elements in this class. The figure shows that europium, iridium and thorium come essentially from the r process, unlike strontium, zirconium, lanthanum and cerium, which originate mainly from the s process. Other elements have more mixed origins. (From Sneden 2001.)... 

In 1901 Eugene-Anatole Demargay in Paris showed that the samples of samarium and gadolinium produced until that time harboured yet another rare-earth element, which he named generously after all of Europe europium. This element is in fact one of the most naturally abundant of the group the Earth s crust contains twice as much europium as tin. It is harvested today largely for a very special and useful property its emission of very pure red and blue light. 

Rare earth element patterns for basalt and chondrite, and the chondrite-normalized basalt REE pattern. Normalization removes the zigzag pattern due to differences in odd and even atomic number abundances. The europium (Eu) anomaly in the normalized pattern is due to incorporation of extra plagiodase. 

Noddack s abundance data 1S] showed 0.25 ppm of europium in chondrites. This is regarded as a very high value. Some recent measurements of Bate et al. [20] by neutron activation analysis of chondrites gave the avarage value of europium content as 0.078 0.003 ppm. Other reported values are 0.187 (Stjess and Ubey [14]), and 0.115 (Cameron... 

Under the same conditions, in contrast to what is observed for calix[4]arene-bearing CMPO moieties, with CPil2, distribution ratios of lanthanides increase from the lightest lanthanide, lanthanum, to europium. Americium can be easily separated from the lightest lanthanides (separation factor DAm/La > 20, DAm/Ce =15, /lAlll,Nd = 10, UAi /si = 7.5, DAm/Eu = 6), which are the most abundant lanthanides in fission-product solution. Cavitands bearing picolinamide (Cv5) or thiopicolin-amide (Cv6) residues seems much less selective than their calixarene counterparts, giving SAm/Eu < 2.18... 

Europium is a metallic element discovered in 1901 in Paris by the French scientist Eugene-Anatole Demarcay. It belongs to a series of elements called lanthanides, or 4f elements, extending from lanthanum (atomic number 57) to lutetium (atomic number 71). These elements have low abundances Europium occurrence in Earth s crust is only 2.1 ppm (parts per million), that is, 2.1 grams (0.07 ounces) per metric ton, and in seawater, its concentration is as low as 4 X 10 8 ppm. 

The element europium exists in nature as two isotopes 151Eu has a mass of 150.9196 amu, and 153Eu has a mass of 152.9209 amu. The average atomic mass of europium is 151.96 amu. Calculate the relative abundance of the two europium isotopes. 

Europium behaves differently, presumably owing to photochemical reduction which makes it be enriched or deposited rather together with alkahne earths, not Ln + species. Note the large differences between Eu and its two direct neighbour elements Sm and Gd. Correlation coefficients for abundances among different plant species are taken from Markert (1996). 

The evidence for this is provided by an increase in the ratio of barium (the abundance of which in galactic matter is dominated by s-process contributions) to europium (almost exclusively an r-process product). The ratio [Ba/Eu] is shown in Figure 9 as a function of [Fe/H] for a large sample of halo and disk stars. Note that at the lowest metallicities the [Ba/Eu] ratio clusters around the pure r-process value ([Ba/Eu]r-process —0-9) at a metallicity [Ee/H]—2.5, the Ba/Eu ratio... 

Itqiy is distinct from chondritic meteorites in bulk composition. Aluminum, FREE, europium, sodium, potassium, vanadium, chromium, and manganese are aU depleted. Itqiy has La/Yb of 0. lOxCI, and Eu/Sm of 0.16 X Cl. Refractory siderophile elements are enriched —2-3 X Cl, while moderately volatile siderophile elements are at roughly Cl abundances. The bulk rock Mg/Si and Fe/Si ratios are greater than those of EH or EL chondrites. 

Europium is not abundant in Earth s surface. It is thought to occur at a concentration of no more than about one part per million. That makes it one of the least abundant of the rare earth elements. The study of light from the sun and certain stars indicates that europium is present in these bodies as well. 

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