One of the simplest and best known kinds of crystal is the ionic salt, of which a typical example is sodium chloride, or ordinary table salt. The fundamental components of an ionic salt are ions: atoms or molecules that have become electrically charged by gaining or losing one more electrons. In forming sodium chloride, for example, sodium atoms give up an electron (thereby becoming, positively charged) and chlorine atoms gain an electron (thereby becoming negatively changed). The ions are attracted to one another by their opposite charges, and they stack together compactly, like tightly packed spheres.
Recently, scientists at Michigan State University created a new kind of crystal called an electride. In electrides, the anions (negative ions) are completely replaced by electrons, which are trapped in naturally formed cavities within a framework of regularly stacked cations (positive ions). Electrides are the first examples of ionic salts in which all these anionic sites are occupied solely by electrons.
Unlike other types of anions, anionic electrons do not behave as if they were simple charged spheres. In particular, because of their low mass and their tendency to interact with one another over great distances, they cannot be “pinned down” to any one location. Instead, they wander close to and among the atoms lining the cavity and interact with electrons in nearby cavities, perhaps changing places with them.
The properties of an electride depend largely on the distance between the cavities that hold trapped electrons. When the trapped electrons are far apart, they do not interact strongly, and so behave somewhat like an array of isolated negative charges. When they are closer together, they begin to display properties associated with large ensembles of identical particles. When they are still closer, the ensemble properties dominate and the electrons “delocalize”: they are no longer tightly bound within individual cavities but are more or less free to pass through the spaces within the framework of positive ions.
By synthesizing electrides from a variety of materials, one can vary the geometry of the anionic cavities and their relation to the surrounding cations. The resulting properties may make it possible for electrides to become a basis for economically useful new materials and devices. For instance, because the electrons in some electrides are very weakly bound, these crystals could be effective as photosensitive detectors, in which an impinging photon liberates an electron, resulting in a small electric current. The same weak binding could also make electrides useful in solar energy converters and as cathodes in batteries. One obstacle is the tendency of electrides to decompose through reaction with air and water. Researchers are seeking ways to increase their stability.
1. The passage is primarily concerned with discussing _____.
2. In the first paragraph, the author is primarily concerned with ______.
3. It can be inferred from the passage that the differences between the behavior of anionic electrons and normal anions result from which of the following features of electrons, as compared to normal anions?
I. The much lower mass of electrons.
II. The much greater tendency of electrons to interact with one another over large distances.
III. The much greater likelihood of electrons to remain trapped in naturally formed anionic cavities.
4. According to the passage, the defining characteristic of an electride is which of the following?
5. It can be inferred from the passage that anions behaving as “simple charged spheres” (3rd paragraph) could be expected to ____.
问题1选项
A.a way to isolate electrons
B.the characteristics of a new kind of crystal
C.the structure of an ionic salt
D.commercial uses for electrides
E.the properties of ions
问题2选项
A.introducing a variant on the standard atomic theory
B.describing how chlorine atoms can become negatively charged
C.describing some early research at Michigan State University
D.presenting the identifying properties of an electride
E.providing background for the technical discussion to follow
问题3选项
A.I only.
B.II only.
C.I and II only.
D.I and III only.
E.II and III only.
问题4选项
A.Its positive ions are of particularly low mass.
B.Its ions possess identical electrical charges.
C.It contains a framework of regularly stacked ions.
D.Its ions demonstrate strong mutual attraction.
E.Its negative ions consist solely of electrons.
问题5选项
A.readily lose electrons and become positively charged
B.move freely in and out of their cavities
C.respond to photons by liberating electrons
D.stack with other anions to create a regular framework
E.remain fixed relative to their cations
第1题:B
第2题:E
第3题:C
第4题:E
第5题:E
第1题:
1.【选项释义】
The passage is primarily concerned with discussing____. 本文主要讨论____。
A. a way to isolate electrons A. 分隔电子的方法
B. the characteristics of a new kind of crystal B. 一种新型晶体的特性
C. the structure of an ionic salt C. 离子盐的结构
D. commercial uses for electrides D. 电子器件的商业用途
E. the properties of ions E. 离子的性质
【考查点】主旨大意题。
【解题思路】根据本文Para. 2可知,“最近,密歇根州立大学的科学家们发明了一种叫做电子晶体的新型晶体。”下文都是描述该晶体的特点。
【干扰项排除】
A选项“分隔电子的方法”,属于无中生有;
C选项“离子盐的结构”,文中主要讲的是通过离子盐获得的新型晶体的特性结构等,而非离子盐,这里属于张冠李戴;
D选项“电子器件的商业用途”,文中没有涉及,属于无中生有;
E选项“离子的性质”,文中有提到离子,但是并不是主要讲述离子,而是讲晶体,这里属于以偏概全。
2.【选项释义】
In the first paragraph, the author is primarily concerned with____. 在第一段中,作者主要关注____。
A. introducing a variant on the standard atomic theory A. 介绍标准原子理论的一个变体
B. describing how chlorine atoms can become negatively charged B. 描述氯原子如何带负电荷
C. describing some early research at Michigan State University C. 描述密歇根州立大学的一些早期研究
D. presenting the identifying properties of an electride D. 给出电子化合物的识别特性
E. providing background for the technical discussion to follow E. 为接下来的技术讨论提供背景
【考查点】主旨大意题。
【解题思路】根据出处提示词Paragraph 1与题干信息词可定位到Para. 1,该处主要讲离子盐这种晶体的电子变化。从离子盐这种最基本的晶体来引出下文中的新型晶体。因此选E。
【干扰项排除】
A选项“介绍标准原子理论的一个变体”属于无中生有;
B选项“描述氯原子如何带负电荷”,并不是作者主要关注的点,属于本末倒置;
C选项“描述密歇根州立大学的一些早期研究”,第一段并没有讲该大学,属于无中生有;
D选项“给出电子化合物的识别特性”,并没有给出电子化合物的特性,只是拿离子盐做例子,属于无中生有。
3.【选项释义】
It can be inferred from the passage that the differences between the behavior of anionic electrons and normal anions result from which of the following features of electrons, as compared to normal anions?
I. The much lower mass of electrons.
II. The much greater tendency of electrons to interact with one another over large distances.
III. The much greater likelihood of electrons to remain trapped in naturally formed anionic cavities. 从文章中可以推断出,与正常阴离子相比,阴离子电子和正常阴离子之间的行为差异源于电子的下列哪个特征?
1.电子的质量更低。
2. 在很远的距离内电子之间相互作用的更大趋势。
3. 电子被困在自然形成的阴离子空腔中的可能性要大得多。
A. I only. A. 只有1。
B. II only. B. 只有2。
C. I and II only. C. 只有1和2。
D. I and III only. D. 只有1和3。
E. II and III only. E. 只有2和3。
【考查点】事实细节题。
【解题思路】根据题干信息可定位到Para. 3该处讲到“与其他类型的阴离子不同,阴离子电子的行为不像简单的带电球体。特别是,由于它们的质量很低(low mass)”,还讲“它们倾向于在很远的距离内相互作用”。因此1和2 正确。比对选项,C选项恰好是此信息的同义转换,因此C选项正确。
【干扰项排除】
选项3中“电子被困在自然形成的阴离子空腔中的可能性要大得多”,文中提到“电子体的特性很大程度上取决于容纳被捕获电子的空腔之间的距离……当它们更接近时,整体性质占主导地位,电子‘离域’:它们不再被紧紧束缚在单独的空腔内,而是或多或少地在正离子框架内自由通过空间。”换言之,电子没有被困在阴离子空腔中。3选项错误,和原文相悖。A、B、D、E错误。
4. 【选项释义】
According to the passage, the defining characteristic of an electride is which of the following? 根据文章,电子化合物的定义特征是下列哪一个?
A. Its positive ions are of particularly low mass. A. 它的正离子质量特别低。
B. Its ions possess identical electrical charges. B. 它的离子具有相同的电荷。
C. It contains a framework of regularly stacked ions. C. 它包含了一个由有序堆叠的离子组成的框架。
D. Its ions demonstrate strong mutual attraction. D. 它的离子表现出强烈的相互吸引力。
E. Its negative ions consist solely of electrons. E. 它的负离子完全由电子组成。
【考查点】事实细节题。
【解题思路】根据题干信息可定位到Para. 2第二句,该处讲到“在电子化合物中,负离子被电子完全取代”,即它的负离子由电子组成。因此E选项正确。
【干扰项排除】
A选项“它的正离子质量特别低”,文中没有提到,属于无中生有;
B选项“它的离子具有相同的电荷”文中没有提及,属于无中生有;
C选项“它包含了一个由有序堆叠的离子组成的框架”,文中Para. 2提到“这些电子被困在自然形成的空腔中,而这个空腔是由有序堆叠的阳离子组成的”,意思是这个空腔是由有序堆叠的离子组成的,而非电子化合物,该选项张冠李戴;
D选项“它的离子表现出强烈的相互吸引力”,Para. 4中提到“电子化合物的特性很大程度上取决于容纳被捕获电子的空腔之间的距离。当被捕获的电子相距较远时,它们的相互作用就不强烈”,所以它的离子并没有表现出强烈的相互吸引力,该选项属于反向干扰。
5. 【选项释义】
It can be inferred from the passage that anions behaving as “simple charged spheres” (3rd paragraph) could be expected to ________. 从这篇文章可以推断,阴离子的行为是“简单的带电球体”(第三段),可预知____。
A. readily lose electrons and become positively charged A. 容易失去电子而带正电
B. move freely in and out of their cavities B. 它们可以自由进出空腔
C. respond to photons by liberating electrons C. 通过释放电子对光子作出反应
D. stack with other anions to create a regular framework D. 与其他阴离子堆叠,创建一个规则的框架
E. remain fixed relative to their cations E.相对于它们的阳离子保持不变
【考查点】推理判断题。
【解题思路】题目的重点在于anions behaving as “simple charged spheres”(表现为“简单的带电球体”的阴离子),可以定位到原文Para. 3第一句“与其他类型的阴离子不同,阴离子电子的行为不像是简单的带电球体”,这是一道反向推理题,第一句中的 “do not behave as if...”表明第三段的阴离子电子特点与表现为“简单的带电球体”的阴离子的特点相反,所以要进行反向推理。第二句中该处讲到“它们不能被‘固定’在任何一个位置( “pinned down” to any one location)”可知阴离子电子特点是不能被固定在任何一个位置,则“简单的带电球体”的阴离子可以被固定住。该题选E。
【干扰项排除】
A选项“容易失去电子而带正电”,文中没有涉及,属于无中生有;
B选项“它们可以自由进出空腔”,阴离子电子可以进出空腔,但是阴离子不可以,属于张冠李戴;
C选项“通过释放电子对光子做出反应”,阴离子电子与附近空腔内的电子相互作用,而不是阴离子,属于张冠李戴。
D选项“与其他阴离子堆叠,创建一个规则的框架”,文中提到“空腔是由有序堆叠的阳离子(正离子)组成的”而不是阴离子电子与阴离子堆叠创建框架,属于无中生有。
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