Where do Transition Elements Come From

Isotopes are nuclides which I lave the same number of Ijroiuns. but different numbers of neutrons, in their nuclei. An isotope is defined by two numbe s the mass number. A, which is total number of nucleons I protons and neutrons) in the nucleus, and the atomic number, Z, which is total nunber of protons in the nucleus. The value of A is written as a. superscript and of Z as a subscript proceeding the element symbol, e.g. Mo. U, - Pu. 

The development of cyclotrons and nuclear reactors in the middle of the 20th century made possible the production of radioactive isotopes which are not naturally present in any significant quantity on Earth. Thus in a nuclear reactor some of the neutrons released by uranium fission may be absorbed by leading to the formation of Pu. 

Similarly, the irradiation of molybdenum with neutrons gives Mo which decays to the metastable y-ray emitting nuclide Tc. This is of great 

Such methods have allowed all the elements of the 6d series, i.e. to Z = 112, to be produced. However, these heavy elements are not available in sufficient quantities for conventional chemical studies and so will not be considered further here. Beyond fermium, even the longest-lived isotopes of the elements are highly radioactive, having only short half-lives (e.g. 53 d for Md, 185 s for No and 45 s for Lr). 

The abundances in the Earth s crust of both the d-block transition metals and the f-block inner transition metals vary considerably, as shown in Table 1.2. Iron is the most common of the transition metals (6.30% by mass of the crustal rocks) and this reflects the high yield of iron from element synthesis reactions in stellar supernovae. Titanium (0.66%) and manganese (0.11%) are also quite abundant, but some of the heavier 

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