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托福閱讀TPO16閱讀原文

The periodic table is a chart that reflects the periodic recurrence of chemical and physical properties of the elements when the elements are arranged in order of increasing atomic number (the number of protons in the nucleus). It is a monumental scientific achievement, and its development illustrates the essential interplay between observation, prediction, and testing required for scientific progress. In the 1800's scientists were searching for new elements. By the late 1860's more than 60 chemical elements had been identified, and much was known about their descriptive chemistry. Various proposals were put forth to arrange the elements into groups based on similarities in chemical and physical properties. The next step was to recognize a connection between group properties (physical or chemical similarities) and atomic mass (the measured mass of an individual atom of an element). When the elements known at the time were ordered by increasing atomic mass, it was found that successive elements belonged to different chemical groups and that the order of the groups in this sequence was fixed and repeated itself at regular intervals. Thus when the series of elements was written so as to begin a new horizontal row with each alkali metal, elements of the same groups were automatically assembled in vertical columns in a periodic table of the elements. This table was the forerunner of the modern table.

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.

Mendeleyev went further than Meyer in another respect: he predicted the properties of six elements yet to be discovered. For example, a gap just below aluminum suggested a new element would be found with properties analogous to those of aluminum. Mendeleyev designated this element "eka-aluminum" (eka is the Sanskrit word for "next") and predicted its properties. Just five years later an element with the proper atomic mass was isolated and named gallium by its discoverer. The close correspondence between the observed properties of gallium and Mendeleyev’s predictions for eka-aluminum lent strong support to the periodic law. Additional support came in 1885 when eka-silicon, which had also been described in advance by Mendeleyev, was discovered and named germanium.

The structure of the periodic table appeared to limit the number of possible elements. It was therefore quite surprising when John William Strut (Lord Rayleigh, discovered a gaseous element in 1894 that did not fit into the previous classification scheme. A century earlier, Henry Cavendish had noted the existence of a residual gas when oxygen and nitrogen are removed from air, but its importance had not been realized. Together with William Ramsay, Rayleigh isolated the gas (separating it from other substances into its pure state) and named it argon. Ramsay then studied a gas that was present in natural gas deposits and discovered that it was helium, an element whose presence in the Sun had been noted earlier in the spectrum of sunlight but that had not previously been known on Earth. Rayleigh and Ramsay postulated the existence of a new group of elements, and in 1898 other members of the series (neon, krypton, and xenon) were isolated.

托福閱讀TPO16閱讀試題

1.The phrase interplay in the passage (paragraph 1) is closest in meaning to

A.sequence

B.interpretation

C.requirement

D.interaction

2.According to paragraph 1, what pattern did scientists notice when the known elements were written in order of increasing atomic mass?

A.The elements of the group of alkali metals were the first elements in the order of increasing atomic mass.

B.Repetition of the same atomic masses for elements in different groups appeared.

C.Elements with similar chemical properties appeared in the listing at regular intervals.

D.Elements were chemically most similar to those just before and after them in the order.

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

4.What reason does the author provide for the claim that Mendeleyev was bolder than Meyer?(in paragraph 2)

A.Mendeleyev corrected incorrect information Meyer had proposed.

B.Mendeleyev assumed that some information believed to be true about the elements was incorrect.

C.Mendeleyev argued that Meyer had not left enough gaps in the periodic table.

D.Mendeleyev realized that elements were not ordered by atomic mass in the periodic table.

5.According to paragraph 2, why did Mendeleyev suggest changing the atomic mass of indium?

A.Because indium did not fit into the periodic table in the place predicted by its atomic mass.

B.Because there was experimental evidence that the atomic mass that had been assigned to indium was incorrect.

C.Because there was an empty space between cadmium and tin in the periodic table.

D.Because the chemical properties of indium were similar to those of arsenic and selenium.

6.It can be inferred from paragraph 2 that tellurium comes before iodine in the periodic table even though tellurium's atomic mass is slightly greater because

A.iodine is less common than tellurium

B.both iodine and tellurium have no isotopes

C.the chemical behavior of tellurium is highly variable

D.the atomic number of tellurium is smaller than that of iodine

7.The phrase “abundance” in the passage (paragraph 2) is closest in meaning to

A.weight

B.requirement

C.plenty

D.sequence

8.The phrase “analogous to” in the passage (paragraph 3) is closest in meaning to

A.predicted by

B.expected of

C.similar to

D.superior to

9.Paragraph 3 suggests that Mendeleyev predicted the properties of eka-aluminum on the basis of

A.the atomic mass of aluminum

B.the position of the gap in the periodic table that eka-aluminum was predicted to fill

C.the similarity of eka-aluminum to the other five missing elements

D.observation of the properties of gallium

10.It can be inferred from paragraph 3 that the significance of the discovery of gallium was that it supported which of the following?

A.The idea that aluminum was correctly placed in the periodic table.

B.Mendeleyev's prediction that eka-silicon would be discovered next.

C.The organizing principle of the periodic table.

D.The idea that unknown elements existed.

11.Which of the sentences below best expresses the essential information in the highlighted sentence in the passage (paragraph 4)? Incorrect choices change the meaning in important ways or leave out essential information.

A.Ramsay found evidence of helium in the spectrum of sunlight before he discovered that the element was also contained in natural gas deposits on Earth.

B.Ramsay thought he had discovered a new element present in natural gas deposits, but he was wrong since that element had been previously observed elsewhere on Earth.

C.After Ramsay had discovered a new element, called helium, in natural gas deposits on Earth, he also found evidence of its presence in the Sun.

D.Ramsay later discovered that helium, an element that was already known to be present in the Sun, was also present in natural gas deposits on Earth.

12.The word “postulated” in the passage (paragraph 4) is closest in meaning to

A.hypothesized

B.discovered

C.reported

D.generated

13. Look at the four squares [■] that indicate where the following sentence could be added to the passage. Where would the sentence best fit? It was a natural Idea to break up the series of elements at the points where the sequence of chemical groups to which the elements belonged began to repeat itself.

Paragraph1: The periodic table is a chart that reflects the periodic recurrence of chemical and physical properties of the elements when the elements are arranged in order of increasing atomic number (the number of protons in the nucleus). It is a monumental scientific achievement, and its development illustrates the essential interplay between observation, prediction, and testing required for scientific progress. In the 1800's scientists were searching for new elements. By the late 1860's more than 60 chemical elements had been identified, and much was known about their descriptive chemistry. Various proposals were put forth to arrange the elements into groups based on similarities in chemical and physical properties. ■【A】The next step was to recognize a connection between group properties (physical or chemical similarities) and atomic mass (the measured mass of an individual atom of an element). ■【B】When the elements known at the time were ordered by increasing atomic mass, it was found that successive elements belonged to different chemical groups and that the order of the groups in this sequence was fixed and repeated itself at regular intervals. ■【C】Thus when the series of elements was written so as to begin a new horizontal row with each alkali metal, elements of the same groups were automatically assembled in vertical columns in a periodic table of the elements. ■【D】This table was the forerunner of the modern table.

14. Directions: An introductory sentence for a brief summary of the passage is provided below. Complete the summary by selecting the THREE answer choices that express the most important ideas in the passage. Some sentences do not belong in the summary because they express ideas that are not presented in the passage or are minor ideas in the passage. This question is worth 2 points.

The periodic table introduced by Meyer and Mendeleyev was the forerunner of the modern table of elements.

A.Lord Rayleigh provided evidence that the structure of the I—Ramsay and Lord Rayleigh challenged the importance of the periodic table limited the potential number of elements.

B.Chemical research that Henry Cavendish had done a century earlier.

C.Isotopes of a given element have exactly the same physical properties, but their chemical properties are slightly different.

D. Mendeleyev and Meyer organized the known elements into a F chart that revealed periodic recurrences of chemical and physical properties.

E.Mendeleyev's successful prediction of the properties of then- r unknown elements lent support to the acceptance of the periodic law.

F.In the 1890's, Ramsay and Lord Rayleigh isolated argon and proposed the existence of a new series of elements.

托福閱讀TPO16閱讀答案

1.interplay相互作用，所以D的interaction正確。從單詞本身看，inter表示在……之間，play是起到什么什么作用，所以interplay是相互作用。原句說觀察、預測與實驗相互作用，所以答案是interaction，A順序B解釋C要求都錯。

2.以increasing atomic mass做關鍵詞定位至倒數(shù)第三句，說把元素按照原子量增加的順序排布，發(fā)現(xiàn)相鄰元素屬于不同的族，族的順序是固定的，每隔固定數(shù)量的元素會重現(xiàn)。所以正確答案是C。A的alkali metals，B的same atomic mass原文都沒說;D說相鄰元素性質(zhì)相近與原文相反。

3.修辭目的題，先找到兩個人名，說兩個人都非常有遠見，在周期表中給沒發(fā)現(xiàn)的元素留了空隙，也就是A說的他們足夠自信認為元素周期律適用于所有元素;B的wrong和C的unwilling都跟原文說反;D的disagreement原文沒說。

4.修辭目的題，先找到兩個人名，說門捷列夫比梅伊爾更膽兒大，他推測如果用來在周期表中排序的原子量與元素周期律互相沖突的時候，就說明原子量錯了，也就是選項B說的門捷列夫認為以前被大家所認識到的一些東西是錯的。兩個人的意見是一樣的，只是門捷列夫更進一步，所以A和C說兩者的意見有差異不對;D說不是按原子量排序的錯。

5.以changing the atomic mass of indium做關鍵詞定位至第六句，說由于元素周期表中砷和硒之間沒有空位，所以銦的原子量是錯的。因為前面說如果原子量把元素放錯了位置，就說明原子量是錯的，后一句是為了證明這個觀點的，所以答案是A。B的experimental evidence和D的化學性質(zhì)相似原文都沒說;C有space與原文相反。

6.以tellerium coms before iodine做關鍵詞定位至倒數(shù)第五句for example處，但這句話只是一個例子，所以往前看，說元素不應該嚴格按照原子量排列，而且最后一句又說決定元素化學性質(zhì)的是原子序數(shù)，不是原子量，也就是應該按照原序數(shù)量排列，所以答案D正確。A誰common誰不common，B有沒有同位素還有C的化學性質(zhì)多變沒有信息能推出。

7.abundance豐度，答案是plenty。原句說這種異常，也就是盡管原子量大卻排在前面這種異常是由于同位素的什么，然后后面就解釋每種同位素的原子序數(shù)相同，但中子數(shù)不同，導致原子量不同，猜到每種同位素的多少不同，所以答案plenty，B要求D順序明顯不對;A重量不同原文已經(jīng)直接說了不用再說一遍。

8.analogous to可類比的，相似的，所以答案similar to正確。原句說鋁元素之下的空格表明一個性質(zhì)與鋁怎么樣的元素的存在，前文都說了相鄰的元素屬于不同的族，而且族會相隔固定數(shù)目的元素出現(xiàn)，而且根據(jù)常識也知道元素周期表中上下兩元素性質(zhì)相似，所以答案是similar。A實現(xiàn)預測的是人，不是鋁元素的性質(zhì);B期待不靠譜;D誰比誰好原文沒說。

9.以eka-aluminum做關鍵詞定位至第三句，但這句話只說了預測了eka的性質(zhì)，沒說根據(jù)什么預測的，看上一句，說eka是鋁之下的那個空格里的元素，而且跟鋁性質(zhì)相似，所以答案是B，eka要填的那個空格。A鋁的原子量C另外五個沒發(fā)現(xiàn)的元素D的gallium原文都沒說。

10.gallium做關鍵詞定位至倒數(shù)第三句，但這句話只是說命名為GA，沒說支持什么，往下看說GA的發(fā)現(xiàn)支持了元素周期律，而問題剛好是問GA的發(fā)現(xiàn)支持了什么，所以答案是C，元素周期表的組成規(guī)律，也就是元素周期律。

11.原文的結(jié)構(gòu)是R研究了一種氣體，并且發(fā)現(xiàn)這種氣體是氦，所以答案是D。A完全搞亂了原文的結(jié)構(gòu)，氦在太陽光譜中不是R發(fā)現(xiàn)的;B的轉(zhuǎn)折關系錯;C和A的錯誤相似，氦在太陽光譜中不是R發(fā)現(xiàn)的。

12.postulate推斷，推測，所以hypothesize正確。原句說這兩個人怎么樣一個新的元素族的存在，接著后面的人分離出了這些元素，既然是后面的人分離的，discover和report就不對，因為這兩個詞有他們兩個發(fā)現(xiàn)的意思;generate完全不對，這兩個人不能產(chǎn)生元素。

13.三個過渡點，分別是名詞chemical groups，名詞sequence和動詞詞組repeat itself，這幾個點都可以確定B或者C是答案，但B前后的atomic mass說明兩句話的過渡是非常緊密的，所以B被排除，答案是C。

14.Lord選項錯，原文沒說他的研究提供了元素周期表限制元素數(shù)量的證據(jù)，不選。Ramsay and Lord選項錯，原文沒說他們倆挑戰(zhàn)了卡文迪許，不選。Isotopes選項是原文第二段中的一個細節(jié)，不選。Mendeleyev and Meyer選項對應原文第一段后半部分，正確。Mendeleyev’s選項對應原文第三段最后兩句，正確。In the 1890’s選項對應全文最后一句話，正確。

托福閱讀TPO16閱讀譯文

　　元素周期表是按原子序數(shù)(元素原子核中質(zhì)子的數(shù)量)由小到大依次排列，反映化學周期性和元素的物理特征的圖表。這一科學發(fā)現(xiàn)具有里程碑的意義，它進一步證明了科學探索過程中觀察、預測和實證之間的根本聯(lián)系。19世紀一開始，科學家們不斷探索新的元素。到19世紀60年代后期，已經(jīng)發(fā)現(xiàn)了60種以上的化學元素，而許多描述性化學被認知。人們提出各種建議，認為該基于化學和物理特征的相似性將化學元素排列成組。他們接下來又證實了元素的族群特性(物理或是化學相似性)和原子質(zhì)量(一種元素的單個原子的測量質(zhì)量)之間存在聯(lián)系。當時元素還是按照原子質(zhì)量從小到大排列，人們發(fā)現(xiàn)，一些具備連續(xù)性的元素卻分屬不同的化學組，并且發(fā)現(xiàn)在這種排列方式下，元素群組的順序是固定的且定期重復。因此，當每一新行都以堿性金屬元素開始并逐步將這一系列的元素排列出來時，元素周期表中同一組中的元素就會自動歸入一個垂直縱列中。這個表格就是現(xiàn)代元素周期表的雛形。

　　當?shù)聡瘜W家邁耶(Lother Meyer)和(彼此獨立的)俄國化學家門捷列夫在1869年到1870年間首次發(fā)布元素周期表時，有三分之一的天然化學元素還沒被發(fā)現(xiàn)。然而這兩位化學家都極富遠見，他們在周期表上留白，對元素物理性和化學性的分析空白處還有新的元素有待發(fā)現(xiàn)。門捷列夫比邁耶更為大膽，他甚至做出假設，如果周期表按原子質(zhì)量排列，但元素位置不對的話，那么原子質(zhì)量也是錯的。在某些情況下，這個設想是正確的。以銦為例，先前測量出銦的原子質(zhì)量在砷和硒之間。但是因為在周期表中這兩個元素之間沒有縫隙，由此門捷列夫提出銦的原子質(zhì)量變?yōu)榻厝徊煌囊粋€值，這樣就可以將其置于鎘和錫之間的空位。事實上，接下來的研究表明，元素周期表中元素不能嚴格按照原子質(zhì)量排列。例如，盡管碲的原子質(zhì)量比碘略大，但在元素周期表中，它卻排在碘前面。出現(xiàn)這種反?，F(xiàn)象，主要是因為相對豐富的“同位素 ”或者各種元素的多樣性。同一元素的所有同位素具有相同的質(zhì)子數(shù)，但中子數(shù)不同，因此它們的原子質(zhì)量也不一樣。一個特定元素的同位素具有相同的化學特征，但在物理性質(zhì)上有一些細微差異?，F(xiàn)在我們知道，是原子數(shù)目(原子核中質(zhì)子的數(shù)量)而非原子質(zhì)量(質(zhì)子和中子的數(shù)量)決定著元素的化學性質(zhì)。

　　門捷列夫在另一個研究上也比邁耶更為深入：他預測還有六種元素的性質(zhì)待被發(fā)現(xiàn)。例如，就在鋁下面有一個空位，這表明還有一個性質(zhì)和鋁類似的新元素存在。門捷列夫?qū)⒃撛囟x為“鋁下元素 ”(eka是梵語詞，意思是 “下一個”)并且還預測了其性質(zhì)。僅僅5年之后，原子質(zhì)量相吻合的元素就被分離出來，發(fā)現(xiàn)者將其命名為“鎵”。鎵所表現(xiàn)出的特性和門捷列夫?qū)Α颁X下元素”的預測一一對應，這為元素法則提供了一個強有力的依據(jù)。還有一個例證，1885年發(fā)現(xiàn)“硅下元素”，同樣為門捷列夫所預測，后來命名為鍺。

　　元素周期表的框架似乎限制了可能存在的元素數(shù)量。因此，當約翰?威廉姆?斯特拉特(瑞利男爵)，在1894年發(fā)現(xiàn)一種氣態(tài)元素不能適應之前的元素表時會非常驚訝。一個世紀以前，亨利?卡文迪許就注意到，當氧氣和氮氣從空氣中被移除后仍然有殘余氣體存在，但當時沒人意識到其中的重要性。瑞利和威廉?拉姆齊一道，共同分離出一種氣體(將之與其他物質(zhì)隔離并存于一個真空環(huán)境)并將其命名為氬。拉姆齊經(jīng)過研究又發(fā)現(xiàn)了另一種存在于自然界中的氣體元素——氦，該元素在太陽中存在，并且很早就被發(fā)現(xiàn)存在于太陽光譜中，但是之前并沒有在地球上找到過。瑞利和拉姆齊做出假設，認為存在一組新元素， 1898年，這一系列元素中的其他元素(氖，氪，氙)也被成功分離出來。

　　具有相同質(zhì)子數(shù)，不同中子數(shù)(或不同質(zhì)量數(shù))同一元素的不同核素互為同位素(Isotopes)。

　　Eka是一個用來為在元素周期表中位于某個元素下面的位置的化學元素命名的前綴。前綴eka-尤其用于命名尚未發(fā)現(xiàn)的元素。例如，在發(fā)現(xiàn)鍺以前它被稱為硅下元素(eka-硅，ekasilicon)。

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