段落1
NARRATOR
Listen to part of a lecture in a chemistry class. The professor has been discussing the periodic table of elements.
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段落2
MALE PROFESSOR
So … are there any questions?
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段落3
FEMALE STUDENT
Yes, em, professor Harrison, you were saying that the periodic table is predictive [hesitant upspeak]? What exactly does that mean?
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I mean I understand how it organizes the elements, but … where is the prediction?
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段落4
MALE PROFESSOR
OK, let's look at periodic table again.
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OK, it groups elements into categories that share certain properties, right?
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段落5
FEMALE STUDENT
Um-huh~
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段落6
MALE PROFESSOR
And it's arranged according to increasing atomic number, which is … ? [prompting for answer]
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段落7
FEMALE STUDENT
The number of protons in each atom of an element.
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段落8
MALE PROFESSOR
Right, well, early versions of the periodic table had gaps, missing elements.
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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.
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And its location in the table would tell you what properties it should have.
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It was really pretty exciting for scientists at that time to find these missing elements and confirm their predictive properties.
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段落9
Um actually, that reminds me of a, of a, of a very good example of all this … element 43.
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See on the table, the symbols for element 42 and 44.
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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.
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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.
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段落10
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.
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段落11
MALE STUDENT
Um, professor Harrison, then, how come in my periodic table, here, element 43 is “Tc”, that's technetium, right?
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段落12
MALE PROFESSOR
OK, let me add that …[writing “technetium” on blackboard]
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Actually, um, that's the point I'm coming to.
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Hardly anyone believed that Tack has discovered the new element.
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X-ray spectroscopy was a new method at that time.
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And they were never able to isolate enough masurium to have a weighable sample, to convince everyone of their discovery, so they were discredited.
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段落13
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]
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段落14
MALE STUDENT
43 Protons?
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段落15
MALE PROFESSOR
That's right, but they named it Technetium to emphasize that it was artificially created with technology.
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And people thought that synthesizing this element, making it artificially was the only way to get it.
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We still haven't found it occurring in nature.
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Now, element 43 what they called Masurium or Technetium is radioactive.
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Why is that matter? What's true of radioactive element?
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段落16
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?
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段落17
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 …
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[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?
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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.
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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.
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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.
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段落18
And you know, here is an incredible irony.
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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.
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段落19
MALE STUDENT
So is my version of the periodic table wrong? Should element 43 really be called Masurium?
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段落20
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.
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They didn't, um, publish enough detail on their methods or instruments for us to know for sure.
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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.
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And of course, it was an element the periodic table let us to expect existed before anyone had found it or made it.
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显示译文 -显示原文 =NARRATOR:
Listen to part of a lecture in a chemistry class. The professor has been discussing the periodic table of elements.
点击显示原文 =旁白:听一段化学课的讲座。教授在讨论元素周期表。 -
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显示译文 -显示原文 =MALE PROFESSOR:
So … are there any questions?
点击显示原文 =教授:大家有什么问题吗? -
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显示译文 -显示原文 =FEMALE STUDENT:
Yes, em, professor Harrison, you were saying that the periodic table is predictive [hesitant upspeak]? What exactly does that mean?
点击显示原文 =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? -
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显示译文 -显示原文 =I mean I understand how it organizes the elements, but … where is the prediction?
点击显示原文 =我明白它如何组织这些元素,但是预测在哪里呢? -
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显示译文 -显示原文 =MALE PROFESSOR:
OK, let's look at periodic table again.
点击显示原文 =教授:好的,让我们再看一下周期表。 -
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显示译文 -显示原文 =OK, it groups elements into categories that share certain properties, right?
点击显示原文 =它把元素按它们共有的特质分类对吗? -
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显示译文 -显示原文 =FEMALE STUDENT:
Um-huh~
点击显示原文 =学生:是的。 -
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显示译文 -显示原文 =MALE PROFESSOR:
And it's arranged according to increasing atomic number, which is … ? [prompting for answer]
点击显示原文 =教授:它按原子数递增排序,原子数是。。。 -
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显示译文 -显示原文 =FEMALE STUDENT:
The number of protons in each atom of an element.
点击显示原文 =学生:是元素原子中的质子数。 -
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显示译文 -显示原文 =MALE PROFESSOR:
Right, well, early versions of the periodic table had gaps, missing elements.
点击显示原文 =教授:对,早期版本的周期表有空缺,丢失的元素。 -
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显示译文 -显示原文 =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.
点击显示原文 =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。 -
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显示译文 -显示原文 =And its location in the table would tell you what properties it should have.
点击显示原文 =它在表中的位置可以告诉我们它应该拥有的特性。 -
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显示译文 -显示原文 =It was really pretty exciting for scientists at that time to find these missing elements and confirm their predictive properties.
点击显示原文 =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。 -
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显示译文 -显示原文 =Um actually, that reminds me of a, of a, of a very good example of all this … element 43.
点击显示原文 =事实上,这让我想起来一个非常好的例子,第43号元素。 -
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显示译文 -显示原文 =See on the table, the symbols for element 42 and 44.
点击显示原文 =看表格中42号及44号元素的符号。 -
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显示译文 -显示原文 =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.
点击显示原文 =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。 -
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显示译文 -显示原文 =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.
点击显示原文 =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。 -
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显示译文 -显示原文 =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.
点击显示原文 =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。 -
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显示译文 -显示原文 =MALE STUDENT:
Um, professor Harrison, then, how come in my periodic table, here, element 43 is “Tc”, that's technetium, right?
点击显示原文 =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? -
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显示译文 -显示原文 =MALE PROFESSOR:
OK, let me add that …[writing “technetium” on blackboard]
点击显示原文 =教授:好吧,我补充一下... -
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显示译文 -显示原文 =Actually, um, that's the point I'm coming to.
点击显示原文 =实际上,我马上要讲到这点。 -
22 / 44
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显示译文 -显示原文 =Hardly anyone believed that Tack has discovered the new element.
点击显示原文 =当时几乎没有人相信Tack发现了新元素。 -
23 / 44
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显示译文 -显示原文 =X-ray spectroscopy was a new method at that time.
点击显示原文 =因为那时X射线光谱学是新方法。 -
24 / 44
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显示译文 -显示原文 =And they were never able to isolate enough masurium to have a weighable sample, to convince everyone of their discovery, so they were discredited.
点击显示原文 =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。 -
25 / 44
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显示译文 -显示原文 =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]
点击显示原文 =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。。。 -
26 / 44
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显示译文 -显示原文 =MALE STUDENT:
43 Protons?
点击显示原文 =学生:43个质子? -
27 / 44
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显示译文 -显示原文 =MALE PROFESSOR:
That's right, but they named it Technetium to emphasize that it was artificially created with technology.
点击显示原文 =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。 -
28 / 44
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显示译文 -显示原文 =And people thought that synthesizing this element, making it artificially was the only way to get it.
点击显示原文 =人们认为人工合成这一元素是唯一得到它的方法。 -
29 / 44
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显示译文 -显示原文 =We still haven't found it occurring in nature.
点击显示原文 =我们至今无法在自然界中找到它。 -
30 / 44
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显示译文 -显示原文 =Now, element 43 what they called Masurium or Technetium is radioactive.
点击显示原文 =43号元素无论称为Masurium还是Technetium,是具有放射性的。 -
31 / 44
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显示译文 -显示原文 =Why is that matter? What's true of radioactive element?
点击显示原文 =这有什么关系呢?放射性元素的是怎样的呢? -
32 / 44
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显示译文 -显示原文 =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?
点击显示原文 =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? -
33 / 44
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显示译文 -显示原文 =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 …
点击显示原文 =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。 -
34 / 44
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显示译文 -显示原文 =[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?
点击显示原文 =所以那时发现Masurium的人显然错了,而发现Technetium的人是对的。是吧? -
35 / 44
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显示译文 -显示原文 =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.
点击显示原文 =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。 -
36 / 44
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显示译文 -显示原文 =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.
点击显示原文 =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。 -
37 / 44
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显示译文 -显示原文 =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.
点击显示原文 =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。 -
38 / 44
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显示译文 -显示原文 =And you know, here is an incredible irony.
点击显示原文 =你们知道么,这很讽刺。 -
39 / 44
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显示译文 -显示原文 =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.
点击显示原文 =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。 -
40 / 44
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显示译文 -显示原文 =MALE STUDENT:
So is my version of the periodic table wrong? Should element 43 really be called Masurium?
点击显示原文 =学生:所以是我们这版的周期表错了?43号元素应该称为Masurium? -
41 / 44
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显示译文 -显示原文 =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.
点击显示原文 =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。 -
42 / 44
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显示译文 -显示原文 =They didn't, um, publish enough detail on their methods or instruments for us to know for sure.
点击显示原文 =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。 -
43 / 44
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显示译文 -显示原文 =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.
点击显示原文 =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。 -
44 / 44
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显示译文 -显示原文 =And of course, it was an element the periodic table let us to expect existed before anyone had found it or made it.
点击显示原文 =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。
- 单句循环:关
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- 单句循环:∞