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托福阅读词汇题：abundance&weight

2015-08-25 10:50:12来源：网络

　　【托福阅读词汇题：abundance&weight】新托福TPO阅读中，词汇题是重要托福阅读题型。托福阅读词汇题做题需要考生掌握一定的词汇量和做题技巧。本文中新东方在线托福网汇总了新托福阅读词汇150题：abundance&weight。

　　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. 【TPO16- Development of the Periodic Table】

　　7. The phrase “abundance” in the passage is closest in meaning to (3)

　　○weight

　　○requirement

　　○plenty

　　○sequence

　　答案见下一页：

本文关键字: 新托福阅读 托福阅读词汇 托福词汇题

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