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第1段

1 .<-NARRATOR:->Listen to part of a lecture in a chemistry class. The professor has been discussing the periodic table of elements.

旁白:听一段化学课的讲座。教授在讨论元素周期表。

第2段

1 .<-MALE PROFESSOR:->So … are there any questions?

教授:大家有什么问题吗?

第3段

1 .<-FEMALE STUDENT:->Yes, em, professor Harrison, you were saying that the periodic table is predictive [hesitant upspeak]? What exactly does that mean?

学生:Harrison教授,你说元素周期表是可预测的?那究竟是什么意思?

2 .I mean I understand how it organizes the elements, but … where is the prediction?

我明白它如何组织这些元素,但是预测在哪里呢?

第4段

1 .<-MALE PROFESSOR:->OK, let's look at periodic table again.

教授:好的,让我们再看一下周期表。

2 .OK, it groups elements into categories that share certain properties, right?

它把元素按它们共有的特质分类对吗?

第5段

1 .<-FEMALE STUDENT:->Um-huh~

学生:是的。

第6段

1 .<-MALE PROFESSOR:->And it's arranged according to increasing atomic number, which is … ? [prompting for answer]

教授:它按原子数递增排序,原子数是。。。

第7段

1 .<-FEMALE STUDENT:->The number of protons in each atom of an element.

学生:是元素原子中的质子数。

第8段

1 .<-MALE PROFESSOR:->Right, well, early versions of the periodic table had gaps, missing elements.

教授:对,早期版本的周期表有空缺,丢失的元素。

2 .Every time you have one more proton you have another element, and then — oops — there’d be an atomic number for which there was no known element. And the uh prediction was that an element with that atomic number existed somewhere, but it just hadn’t been found yet.

多一个质子,就成了另一种元素。但是有相应的原子数,却不知道相应的元素是什么。预测正是指那个原子数确定但还仍未被发现的元素。

3 .And its location in the table would tell you what properties it should have.

它在表中的位置可以告诉我们它应该拥有的特性。

4 .It was really pretty exciting for scientists at that time to find these missing elements and confirm their predictive properties.

对那个时候的科学家来说找到这些缺失的元素并确认它们预测特性是件很令人激动的事。

第9段

1 .Um actually, that reminds me of a, of a, of a very good example of all this … element 43.

事实上,这让我想起来一个非常好的例子,第43号元素。

2 .See on the table, the symbols for element 42 and 44.

看表格中42号及44号元素的符号。

3 .Well, in early versions of the table, there was no symbol for element 43 protons because no element with 43 protons had been discovered yet.

在早期版本的周期表中,43号元素没有符号,因为那时有43个质子数的元素尚未被发现。

4 .So the periodic table had a gap between elements 42 and 44. And, then, uh, in 1925 a team of chemists led by a scientist named Ida Tacke claimed that they had found element 43.

所以周期表上在42和44号元素中有空缺,之后在1925年,由一位名叫Ida Tack的科学家带领的化学家团队声称他们找到了43号元素。

第10段

1 .They had been, uh, using a relatively new technology called x-ray spectroscopy —and they were using this to examine an ore sample — and they claimed they’d found an element with 43 protons. And they named it masurium.

他们正在使用一项相对较新的技术X射线光谱学检查一种矿石样本,他们称找到了有43个质子的元素,命名为Masuria。

第11段

1 .<-MALE STUDENT:->Um, professor Harrison, then, how come in my periodic table, here, element 43 is “Tc”, that's technetium, right?

学生:Harrison教授,在我们元素周期表中43号元素是Tc是怎么来的呢?那是锝对吗?

第12段

1 .<-MALE PROFESSOR:->OK, let me add that …[writing “technetium” on blackboard]

教授:好吧,我补充一下...

2 .Actually, um, that's the point I'm coming to.

实际上,我马上要讲到这点。

3 .Hardly anyone believed that Tack has discovered the new element.

当时几乎没有人相信Tack发现了新元素。

4 .X-ray spectroscopy was a new method at that time.

因为那时X射线光谱学是新方法。

5 .And they were never able to isolate enough masurium to have a weighable sample, to convince everyone of their discovery, so they were discredited.

他们无法分离出足够多的Masurium作为使人信服的样本,所以他们没有被人们相信。

第13段

1 .But then, twelve years later, in 1937, a different team became the first to synthesize an element using a cyclotron. And that element had … [dramatic pause, leading the students to answer]

但是后来,12年后,1937年,另一支队伍成为首次使用回旋加速器合成元素的团队。合成这种元素有。。。

第14段

1 .<-MALE STUDENT:->43 Protons?

学生:43个质子?

第15段

1 .<-MALE PROFESSOR:->That's right, but they named it Technetium to emphasize that it was artificially created with technology.

教授:对,但是他们将它命名为Technetium以强调它是由技术人工合成的。

2 .And people thought that synthesizing this element, making it artificially was the only way to get it.

人们认为人工合成这一元素是唯一得到它的方法。

3 .We still haven't found it occurring in nature.

我们至今无法在自然界中找到它。

4 .Now, element 43 what they called Masurium or Technetium is radioactive.

43号元素无论称为Masurium还是Technetium,是具有放射性的。

5 .Why is that matter? What's true of radioactive element?

这有什么关系呢?放射性元素的是怎样的呢?

第16段

1 .<-FEMALE STUDENT:->It decays? [adding to her answer] It turns into other elements? Oh [light dawning], so does that explain why it was missing in the periodic table?

学生:放射性元素会衰变,它会转变成其他元素,哦,这是不是解释了为什么它在元素周期表中曾一度缺失?

第17段

1 .<-MALE PROFESSOR:->Exactly. Because of its radioactive decay, element 43 doesn’t last very long … and therefore… if it ever had been present on Earth it would have decayed ages ago …

教授:正是。由于43号元素放射性的衰变,它不能长久存在,因此,如果它曾经在地球上存在过,也早就衰变了。

2 .[Reporting on what people believed then, not what he himself thinks] So the Masurium people were obviously wrong, and the Technetium people were right, right?

所以那时发现Masurium的人显然错了,而发现Technetium的人是对的。是吧?

3 .Well, that was then. Now we know that element 43 does occur naturally—it can be naturally generated from uranium atoms that have spontaneously split.

不过那是以前,现在我们知道43号元素在自然中确实存在,它可以从铀原子自发的裂变中自然产生。

4 .And guess what ... the ore sample the masurium group was working with had plenty of uranium in it—enough to split into measurable amounts of masurium.

猜怎么着?masurium小组研究的矿石样品中含有大量的铀,足够分裂成可测量的masurium。

5 .So Tacke’s team might very well have found small amounts of masurium in their ore sample. It’s just that once it was generated from split uranium, it decayed very quickly.

所以Tack的团队可能真的在矿石样品中发现了小量masurium ,只是它一从铀裂变中产生后就迅速衰变了。

第18段

1 .And you know, here is an incredible irony.

你们知道么,这很讽刺。

2 .Ida Tack, the chemist led the Masurium team, when she was the first to suggest that Uranium could break up into smaller pieces but she didn't know that that was the defense of her own discovery of element 43.

发现Masurium的化学家Ida Tack,她是第一个提出铀可以分解成小片,但她不知道这是对她自己发现的43号元素的辩护。

第19段

1 .<-MALE STUDENT:->So is my version of the periodic table wrong? Should element 43 really be called Masurium?

学生:所以是我们这版的周期表错了?43号元素应该称为Masurium?

第20段

1 .<-MALE PROFESSOR:->Maybe, but you know it‘s hard to tell for sure after all this time, if Ida Tack’s group did discover element 43.

教授:也许,但是你们知道已经过去那么久这很难说Ida Tack 的队伍是否发现了43 号元素。

2 .They didn't, um, publish enough detail on their methods or instruments for us to know for sure.

他们没有发布关于他们使用的方法或是仪器的足够多的细节信息使我们确认。

3 .But I'd like to think that element 43 was discovered twice, as Masurium, it was the first element discovered that occurs in nature only from spontaneous fission, and as Technetium, it was the first element discovered in laboratory.

但是我愿意认为43 号元素被两次发现。作为Masurium,它是首次从自然裂变中发生的自然元素,作为Technetium,它首次在实验室发现。

4 .And of course, it was an element the periodic table let us to expect existed before anyone had found it or made it.

当然,它是一种在被任何人发现或是制造之前,周期表让我们相信它存在的元素。