tailieunhanh - TOXICOLOGICAL CHEMISTRY AND BIOCHEMISTRY - CHAPTER 10

Nó là hơi khó để xác định những gì có nghĩa là một yếu tố độc hại. Một số yếu tố, như phốt pho trắng, clo, và thủy ngân, một chất độc trong trạng thái nguyên tố. Những người khác, chẳng hạn như carbon, nitơ và oxy, là vô hại như thường gặp trong các hình thức nguyên tố bình thường của họ. Tuy nhiên, với ngoại lệ của các khí hiếm không kết hợp hóa học, tất cả các yếu tố có thể hình thành hợp chất độc hại. Một ví dụ điển hình là hydrogen cyanide. Hợp chất. | Chapter 10 Toxic Elements introduction It is somewhat difficult to define what is meant by a toxic element. Some elements such as white phosphorus chlorine and mercury are quite toxic in the elemental state. Others such as carbon nitrogen and oxygen are harmless as usually encountered in their normal elemental forms. But with the exception of those noble gases that do not combine chemically all elements can form toxic compounds. A prime example is hydrogen cyanide. This extremely toxic compound is formed from three elements that are nontoxic in the uncombined form and produce compounds that are essential constituents of living matter but when bonded together in the simple HCN molecule constitute a deadly substance. The following three categories of elements are considered here Those that are notable for the toxicities of most of their compounds Those that form very toxic ions Those that are very toxic in their elemental forms Elements in these three classes are discussed in this chapter as toxic elements with the qualification that this category is somewhat arbitrary. With a few exceptions elements known to be essential to life processes in humans have not been included as toxic elements. toxic elements and the periodic table It is most convenient to consider elements from the perspective of the periodic table which is shown in Figure and discussed in Section . Recall that the three main types of elements based on their chemical and physical properties as determined by the electron configurations of their atoms are metals nonmetals and metalloids. Metalloids B Si Ge As Sb Te At show some characteristics of both metals and nonmetals. The nonmetals consist of those few elements in groups 4A to 7A above and to the right of the metalloids. The noble gases only some of which form a limited number of very unstable chemical compounds of no toxicological significance are in group 8A. All the remaining elements including the lanthanide and actinide series .