托福阅读修辞目的题是阅读考试中比较常见的一种题型，tpo则是托福阅读备考最权威的材料，所以托福小编综合二者，为大家集中整理了tpo阅读中考察的修辞目的题及其对应的解析，供大家参考使用。本文带来的是TPO16-3的修辞目的题，一起来看看吧。
TPO16-3 Development of the Periodic Table
Paragraph 2
When the German chemist Lothar Meyer and (independently) the Russian Dmitry Mendeleyev first introduced the periodic table in 1869-70, one-third of the naturally occurring chemical elements had not yet been discovered. Yet both chemists were sufficiently farsighted to leave gaps where their analyses of periodic physical and chemical properties indicated that new elements should be located. Mendeleyev was bolder than Meyer and even assumed that if a measured atomic mass put an element in the wrong place in the table, the atomic mass was wrong. In some cases this was true. Indium, for example, had previously been assigned an atomic mass between those of arsenic and selenium. Because there is no space in the periodic table between these two elements, Mendeleyev suggested that the atomic mass of indium be changed to a completely different value, where it would fill an empty space between cadmium and tin. In fact, subsequent work has shown that in a periodic table, elements should not be ordered strictly by atomic mass. For example, tellurium comes before iodine in the periodic table, even though its atomic mass is slightly greater. Such anomalies are due to the relative abundance of the "isotopes" or varieties of each element. All the isotopes of a given element have the same number of protons, but differ in their number of neutrons, and hence in their atomic mass. The isotopes of a given element have the same chemical properties but slightly different physical properties. We now know that atomic number (the number of protons in the nucleus), not atomic mass number (the number of protons and neutrons), determines chemical behavior.
3. In paragraph 2. what is the author's purpose in presenting the information about the decision by Meyer and Mendeleyev to leave gaps in the periodic table?
A. To illustrate their confidence that the organizing principles of the periodic table would govern the occurrence of all chemical elements
B. To indicate that some of their analyses of periodic physical and chemical properties were later found to be wrong
C. To support the idea that they were unwilling to place new elements in the periodic table
D. To indicate how they handled their disagreement about where to place new elements
解析：修辞目的题，先找到两个人名，说两个人都非常有远见，在周期表中给没发现的元素留了空隙，也就是A说的他们足够自信认为元素周期律适用于所有元素;B的wrong和C的unwilling都跟原文说反;D的disagreement原文没说
[2] 当德国化学家迈耶(Lother Meyer)和(彼此独立的)俄国化学家门捷列夫在1869年到1870年间首次发布元素周期表时，有三分之一的天然化学元素还没被发现。然而这两位化学家都极富远见，他们在周期表上留白，对元素物理性和化学性的分析空白处还有新的元素有待发现。门捷列夫比迈耶更为大胆，他甚至做出假设，如果周期表按原子质量排列，但元素位置不对的话，那么原子质量也是错的。在某些情况下，这个设想是正确的。以铟为例，先前测量出铟的原子质量在砷和硒之间。但是因为在周期表中这两个元素之间没有缝隙，由此门捷列夫提出铟的原子质量变为截然不同的一个值，这样就可以将其置于镉和锡之间的空位。事实上，接下来的研究表明，元素周期表中元素不能严格按照原子质量排列。例如，尽管碲的原子质量比碘略大，但在元素周期表中，它却排在碘前面。出现这种反常现象，主要是因为相对丰富的“同位素 ”或者各种元素的多样性。同一元素的所有同位素具有相同的质子数，但中子数不同，因此它们的原子质量也不一样。一个特定元素的同位素具有相同的化学特征，但在物理性质上有一些细微差异。现在我们知道，是原子数目(原子核中质子的数量)而非原子质量(质子和中子的数量)决定着元素的化学性质。
以上就是托福阅读TPO16-3中的修辞目的题及其解析，大家可以在备考的时候参考复习，希望能够帮助大家的考前准备。最后前程百利祝大家都能取得理想的托福考试成绩。
您还可能关注：
