英汉双语化学入门汉语翻译.docx

第八章The most popular form of the periodic table is the long form that isfound inside the back cover of this book .The periods consist of those elementsthat are arranged in horizontal rows in the table .The organization is suchthat elements of similar chemical and physical properties ( called groups orfamilies) appear in vertical columns . In this table, the set of elementsappearing at the bottom and called the lanthanides should actually appear inthe body of the chart in proper order by atomic number so that the sixthperiod has its requisite 32 elements .For convenience in reproduction this isnot done; but, properly, the chart should be vertically cut, the sectionsseparated, and the lanthanides inserted in their proper positions .For theactinides,which appear below the lanthanides at the bottom of the periodictable, the same considerations pertain; they should be inserted in the seventhChapter 8 Periodic Law and Electronic Structures l 39 period(as yet incomplete) .The first period consists of only two elements, hydrogen and helium .Subsequent periods have 8, 8, 18, 18, and 32 elements .With the exception ofthe first period, each complete period begins with an alkali metal ( group A)a highly reactive, light , silvery metaland ends with a noble gas( group0 )an unreactive, colorless gas .The element before the noble gas of eachcomplete period(again, excepting the first period) is a halogen( group A)avery reactive nonmetal .There is a general pattern for each of the periods after the first .Startingwith an alkali metal , the properties change from element to elementthemetallic properties fading and being gradually replaced by nonmetalliccharacteristics .After a highly reactive nonmetal, a halogen, is reached, eachcomplete period ends with a noble gas .Since the periodic table classi fies atoms by chemical behavior, and sincechemical behavior is determined by electronic conf iguration, the periodictable may also be said to classify atoms by electronic configuration . Themaximum number of electrons that each energy level may hold is given by2 n2, where n is the principal quantum number of the shell in question .Hencefor the n = 1 shell, the maximum number is 2 (1 )2or 2 ; for the n = 2 level, thisnumber is 2( 2)2or 8; these maximum electron populations for the first fiveshells are given in table 8 .1 .Table 8 . 1 Maximum Number of Electrons for Each ShellShell n 2 n2K 1 2 yL 2 8 yM 3 18 yN 4 32 yO 5 50 y In this discussion all elements are considered in their ground states .Thefirst element , hydrogen,has one electron in the K level ; the second, helium,has two electrons in this shell .This completes the n = 1 shell and the firstperiod .The third element, lithium,has a complete K shell and one electron inthe L level .Each succeeding element in the period adds one electron to thisl 40 level .The second period ends with the noble gas neon( Z = 10 )which has twoelectrons in the n = 1 level and a complete n = 2 level of eight electrons .A striking fact is encountered in the third period .The initial element ofthis period, sodium,has completed K and L shells of two and eight electrons,respectively, and an additional electron in the next level, the M level( n = 3) .One notes that in the first group of elements, lithium and sodium both haveone electron in the outer shell .Likewise the second elements of these periodsboth have two electrons in their outer shells; beryllium has a configuration( by shells) of 2, 2, and magnesium has a configuration of 2 ,8 ,2 .By comparing the third period elements with the second periodelements, we see that the number of electrons in the outer shells( called thevalence shells) is the same for elements of the same group and that this numberis the same as the group number . This similarity in number of valenceelectrons accounts for the similarities in properties . These facts may bederived f rom table 8 . 2 .这本书的封底内最流行的元素周期表是长时期形成。在这张表上，周期是由被安排在同一行上的元素组成的。又类似的化学和物理性质的元素组成列。在这张表中，元素出现在底部的集称为镧系元素实际上应该按照原子序数排列在图表上，所以第六周期有32个元素。为了便于复制不这样做；但是，正确，图表垂直切割，切片镧系元素的分离，并插入正确的位置。锕系元素，在周期表底部镧系元素的下面，同样的考虑；他们应插在第七周期（但不完全）。第一周期只包含两个元素，氢和氦。随后的周期有8，8，18，18，和32的元素。第一周期的例外，每一个完整的周期开始于碱金属（集团一）-高反应性，光，银色的金属和两端的惰性气体（组0）-一个不活泼的，无色的气体之前。每一个完整的周期的稀有气体元素（再次，除第一期）是一种卤素（集团一）-一个很活泼的非金属。每一周期有一个通用的模式，从碱金属，金属性逐渐降低并逐渐被非金属性取代。到达一个高活性非金属，卤素，每一个完整地周期由惰性气体结束。元素周期表通过化学性质分类，并且通过电子构型决定化学性质，元素周期表也可能说对原子的电子构型进行分类。电子的每个能级的最大数量是2n2，n是电子层的主量子数，因此n=1电子层，最多有2（1）2或2个电子，n=2的电子层，这个数字是2(2)2 或 8，在表8.1中给出了从第一层到第五电子层的最大电子数。在这次讨论中所有的元素都是在基态的考虑。第一个元素，氢，有一个在K级电子；第二，氦，在这个电子层有两个电子。这就完成了N =1电子层和第一周期。第三元素，锂，在L电平的一个完整的K层和L层上的一个电子。在周期上随后的每个元素增加了一个电子到这个层上。第二周期末端是惰性气体氖（Z=10）n =1级两个电子