Uranium in the Environment: Occurrence, Transfer, and Biological Effects

The term metal designates a group of chemical elements mainly found in columns IA, IIA, and among transition elements in the periodic table. They are chiefly known to form basic oxides with oxygen. Considering their biological effects, this group is extremely heterogeneous. In fact, some metals are trace elements; that is, in small amounts they are vital to life (iron, zinc, magnesium, copper, and cobalt). Others are, on the contrary, toxic even in small quantities. This is the case for heavy metals such as cadmium, mercury, and chromium.