门捷列夫定期表格

Look at the left-hand photo above. What a messy closet! Do you have a messy closet too? If you do, then you know how hard it can be to find a specific item of clothing. If you don’t have a messy closet, just imagine trying to find a particular shirt or pair of jeans in the closet above. It could take a long time, and it would probably make you late for school! Now look at the closet on the right. It’s very neat and well organized. With a closet like this, it would be easy to find whatever item you wanted.
::看看上面的左手相片。 多乱的衣柜! 你是否也有一个乱的衣橱? 如果是这样的话,那么你就会知道找到一件具体的衣服有多难。如果你没有一团乱的衣橱,你只要想象一下在上面的衣橱里能找到一件特别的衬衫或牛仔裤。这可能需要很长时间,而且可能会让你迟到上学!现在看看右边的衣橱。这个衣橱非常整齐,组织井然。有了这样的衣橱,很容易找到你想要的东西。

Q: What do these two closets have to do with science ?
::问:这两个衣柜和科学有什么关系?

A: They show why it’s important to keep things organized, including the , which are the pure substances that make up all kinds of matter.
::说明为何必须保持秩序, 包括由纯物质组成的物质。

Organizing Elements
::组织要素

For many years, scientists looked for a good way to organize the elements. This became increasingly important as more and more elements were discovered. An ingenious method of organizing elements was developed in 1869 by a Russian scientist named Dmitri Mendeleev, who is pictured . Mendeleev’s method of organizing elements was later revised, but it served as a basis for the method that is still used today. 
::多年来,科学家们一直在寻找一种组织元素的好方法。 随着越来越多的元素被发现,这一点变得越来越重要。 1869年,一位俄罗斯科学家德米特里·门捷列夫(Dmitri Mendeleev)开发了一种组织元素的巧妙方法。 曼捷列夫组织元素的方法后来被修改,但作为今天仍然使用的方法的基础。

Mendeleev was a teacher as well as a chemist. He was writing a chemistry textbook and wanted to find a way to organize the 63 known elements so it would be easier for students to learn about them. He made a set of cards of the elements, similar to a deck of playing cards. On each card, he wrote the name of a different , its atomic mass, and other known properties. Mendeleev arranged and rearranged the cards in many different ways, looking for a pattern. He finally found it when he placed the elements in order by increasing atomic mass.
::Mendeleev既是一名教师,也是一名化学家。他正在编写一本化学教科书,并想找到一种方法来组织63种已知元素,这样学生更容易了解这些元素。他制作了一套元素卡片,类似于一张扑克牌。每张卡片上他都写下了不同名称、原子质量和其他已知属性。门捷列夫以多种不同的方式安排和重新排列了卡片,寻找一种模式。当他通过增加原子质量来排列元素时,他终于找到了它。

Q: What is atomic mass? Why might it be a good basis for organizing elements?
::问题:什么是原子质量?为什么它可以成为组织元素的良好基础?

A: Atomic mass is the mass of one of an . It is about equal to the mass of the plus the in an . It is a good basis for organizing elements because each element has a unique number of protons and atomic mass is an indirect way of organizing elements by number of protons.
::A:原子质量是其中的一个质量。它大约等于加加加中的质量。它是组织元素的良好基础,因为每个元素都有独特的质子数量,原子质量是按质子数量来组织元素的一种间接方式。

Groups and Periods
::集团和期间

You can see how Mendeleev organized the elements in the Figure . From left to right across each row, elements are arranged by increasing atomic mass. Mendeleev discovered that if he placed eight elements in each row and then continued on to the next row, the columns of the table would contain elements with similar properties. He called the columns groups . They are sometimes called families, because elements within a group are similar but not identical to one another, like people in a family.
::您可以看到 Mendeleev 是如何组织图中元素的 。 从左到右, 元素通过增加原子质量来排列 。 Mendeleev 发现, 如果他在每行中放置八个元素, 然后继续到下一行, 表格的列会包含类似属性的元素 。 他称之为列组 。 它们有时被称为家庭, 因为组合中的元素是相似的, 但和家庭中的人不同。

Mendeleev’s table of the elements is called a periodic table because of its repeating pattern. Anything that keeps repeating is referred to as periodic. Other examples of things that are periodic include the monthly phases of the moon and the daily cycle of night and day. The term period refers to the interval between repetitions. For example, the moon’s phases repeat every four weeks. In a periodic table of the elements, the periods are the rows of the table. In Mendeleev’s table, each period contains eight elements, and then the pattern repeats in the next row.
::Mendeleev的元素表因其重复模式而被称为定期表格。 任何不断重复的都被称为定期。 其他定期的例子包括月亮的月度阶段和日夜的日周期。 术语指的是重复的时间间隔。 例如,月亮的阶段每四个星期重复一次。 在元素的定期表格中,时间段是表格的行。 在Mendeleev的表格中,每个周期包含八个元素,然后在下一行重复模式。

Filling in the Blanks
::填空空空

Did you notice the blanks in Mendeleev’s table? They are spaces that Mendeleev left blank for elements that had not yet been discovered when he created his table. He predicted that these missing elements would eventually be discovered. Based on their position in the table, he even predicted their properties. For example, he predicted a missing element in row 5 of group III. He also predicted that the missing element would have an atomic mass of 68 and be a relatively soft metal like other elements in this group. Scientists searched for the missing element, and they found it just a few years later. They named the new element gallium. Scientists searched for the other missing elements in Mendeleev’s table and eventually found all of them.
::你注意到门捷列夫桌子上的空白吗? 这些空格是门捷列夫在创建桌子时尚未发现的元素留下的空白空间。 他预测这些缺失元素最终会被发现。 根据他们在桌子上的位置,他甚至预测了它们的属性。 例如,他预测第三组第5排的缺失元素。 他还预测,缺失元素将具有68个原子质量,并且像这个组中的其他元素一样是一个相对软的金属。 科学家们寻找了缺失元素,并在几年后发现了它。他们给新元素命名了。 科学家们在门捷列夫的桌子上搜索了其他缺失元素,最终找到了所有元素。

An important measure of a good model is its ability to make accurate predictions. This makes it a useful model. Clearly, Mendeleev’s periodic table was a useful model. It helped scientists discover new elements and made sense of those that were already known.
::衡量一个好模型的一个重要尺度是它是否有能力做出准确的预测。 这使得它成为一个有用的模型。 显然,门捷列夫的周期表是一个有用的模型。 它帮助科学家发现新的元素,并让已知元素变得有意义。

Summary
::摘要

播放段落
• In 1869, Dmitri Mendeleev developed a method for organizing elements based on their atomic mass. His method was later revised, but it served as a basis for the method used today.
  ::1869年,Dmitri Mendeleev开发了基于原子质量的元素组织方法,后来对其方法进行了修改,但作为今天所用方法的基础。
播放段落
• Mendeleev created a periodic table of all the elements that were known at the time. The rows of the table, called periods, each contained eight elements that increased in atomic mass from left to right. The columns of the table, called groups, contained elements with similar properties.
  ::门捷列夫创建了一个定期表格,列出当时已知的所有元素。表格各行称为 " 周期 " ,每行包含八个元素,原子质量从左向右上升。表格各列称为 " 组 " ,包含类似属性的元素。
播放段落
• Mendeleev’s periodic table was a good model because it could be used to predict unknown elements and their properties. All of these missing elements were eventually discovered.
  ::Mendeleev的周期表是一个好样板,因为它可以用来预测未知元素及其属性。 所有这些缺失元素最终都被发现了。

Review
::回顾

播放段落
1. How did Mendeleev develop his periodic table of the elements?
   ::Mendeleev如何编制其元素周期表?
播放段落
2. What are the groups in Mendeleev’s table?
   ::Mendeleev的桌子上是什么群体?
播放段落
3. Describe the periods in Mendeleev’s table.
   ::描述Mendeleev表格中的时期。
播放段落
4. Why was Mendeleev’s periodic table a good model?
   ::为什么门捷列夫的周期表是一个好样板?

Resources
::资源