Samarium history

Marignac s research appeared to be satisfactory for nearly 20 years. Then, another French chemist, Eugene-Anatole Demar ay (1852— 1904), found that samarium could itself be broken into two parts. He called the new elements samarium and europium. Because of this long history, credit for the discovery of samarium is usually given to Boisbaudran, Marignac, Demar ay, or to all three chemists. 

Samarium is named after the mineral samarskite, from which the first traces were found. The history of its discovery is very convoluted, and it is part of the complex yttria group. The first suggestion of a new element came in 1846, but it was not until 1878 that J. Lawrence Smith (1818-1883) announced a new element he called mosandrum. His discovery was disputed, and, in 1879, Francois Lecoq de Boisbaudran named it samaria, which was later changed to samarium. The whitish-silver element does not occur in elemental form in nature. It has been used in lighting systems and also as part of rare-earths magnets, in lasers, in infrared absorbing glass, and in nuclear reactors as a neutron buffer. 

The work of Moseley made clear the existence of an unknown element between neodymium and samarium. But the situation proved to be not so clear and dramatic events rapidly followed in the history of element 61. 

As just mentioned, thirteen lanthanides had been discovered but, according to the new knowledge of the atom, one was missing. In 1914, Moseley confirmed that there must be an element with atomic number 61 between neodymium and samarium. Where was that element in nature Astronomical studies indicated that it is present on the surface of star in the Andromeda galaxy. But all attempts to find it on earth failed. The search had to take quite different paths than had been common in the whole history of lanthanide discovery. 

Describe xenon and samarium transient behavior for the following power histories (1) startup to steady state power ( ) shutdown from steady state (3) startup near peak shutdown concentration (4) decrease in power after prolonged operation at steady state and (5) Increase in power after prolonged operation at steady state,... 

Sketch reactivity versus time for both xenon-135 and samarium-149 with the following power history ... 

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