Periodic Table: Scientists Propose New Way Of Ordering The Elements周期表:科学家提出了排列元素的新方法

The periodic table of the elements, principally created by the Russian chemist, Dmitry Mendeleev (1834-1907), celebrated¹ its 150th anniversary last year. It would be hard to overstate its importance as an organising principle in chemistry – all budding chemists become familiar with it from the earliest stages of their education.

元素周期表主要是由俄国化学家德米特里·门捷列夫(1834-1907)发明的，去年庆祝了它的150周年纪念日。在化学中，它作为一种组织原理的重要性怎么说都不为过——所有刚出道的化学家在他们受教育的最初阶段就已经熟悉它了。

Given the table’s importance, one might be forgiven for thinking that the ordering of the elements were no longer subject to debate. However, two scientists in Moscow, Russia, have recently published a proposal for a new order.

考虑到表的重要性，人们可能会认为元素的顺序不再是辩论的主题，这是可以原谅的。然而，俄罗斯莫斯科的两位科学家最近发表了一份关于新排序的建议。

Let’s first consider how the periodic table was developed. By the late 18th century, chemists were clear about the difference between an element and a compound: elements were chemically indivisible (examples are hydrogen, oxygen) whereas compounds consisted of two or more elements in combination, having properties quite distinct from their component² elements. By the early 19th century, there was good circumstantial evidence for the existence of atoms. And by the 1860s, it was possible to list the known elements in order of their relative atomic mass – for example, hydrogen was 1 and oxygen 16.

让我们首先考虑元素周期表是如何形成的。到18世纪晚期，化学家们已经清楚了元素和化合物之间的区别:元素在化学上是不可分的(例如氢、氧)，而化合物是由两种或两种以上的元素组合而成，具有与其组成元素截然不同的性质。到19世纪初，已经有了很好的间接证据证明原子的存在。到了19世纪60年代，人们可以按照相对原子质量的顺序列出已知元素——例如，氢是1，氧是16。

Simple lists, of course, are one-dimensional in nature. But chemists were aware that certain elements had rather similar chemical properties: for example lithium, sodium³ and potassium or chlorine, bromine and iodine⁴. Something seemed to repeat and by placing chemically similar elements next to each other, a two-dimensional table could be constructed. The periodic table was born.

当然，简单的列表本质上是一维的。但化学家们意识到某些元素具有相当相似的化学性质:例如锂、钠和钾或氯、溴和碘。有些东西似乎是重复的，通过把化学成分相似的元素放在一起，就可以建立一个二维表格。元素周期表诞生了。

Nick Norman

Importantly, Mendeleev’s periodic table had been derived⁶ empirically based on the observed chemical similarities of certain elements. It would not be until the early 20th century, after the structure of the atom had been established and following the development of quantum theory, that a theoretical understanding of its structure would emerge.

重要的是，门捷列夫的元素周期表是根据观察到的某些元素的化学相似性根据经验推导出来的。直到20世纪初，在原子结构被确定之后，随着量子理论的发展，才出现了对原子结构的理论理解。

Elements were now ordered by atomic number (the number of positively⁷ charged particles called protons in the atomic nucleus), rather than by atomic mass, but still also by chemical similarities. But the latter now followed from the arrangement of electrons repeating in so-called “shells” at regular intervals⁸. By the 1940s, most textbooks featured a periodic table similar to ones we see today.

元素现在按原子序数(原子核中被称为质子的带正电的粒子的数量)排序，而不是按原子质量排序，但仍然按化学相似性排序。但现在，电子在所谓的“壳层”中按照一定的间隔重复排列，形成了后者。到20世纪40年代，大多数教科书都有与我们今天看到的元素周期表类似的元素周期表。

It would be understandable to think that this would be the end of the matter. Not so, however. A simple search of the internet will reveal all sorts of versions of the periodic table. There are short versions, long versions, circular versions, spiral versions and even three-dimensional versions. Many of these, to be sure, are simply different ways of conveying the same information but there continue to be disagreements about where some elements should be placed.

认为这件事将就此结束，这是可以理解的。但事实并不是这样的。在互联网上简单地搜索一下，就会发现元素周期表的各种版本。有短版本，长版本，圆形版本，螺旋版本，甚至三维版本。可以肯定的是，其中许多只是传达相同信息的不同方式，但对于某些元素应该放在哪里仍然存在分歧。

The precise placement of certain elements depends on which particular properties we wish to highlight. Thus, a periodic table which gives primacy to the electronic structure of atoms will differ from tables for which the principal criteria⁹ are certain chemical or physical properties.

某些元素的精确位置取决于我们希望突出显示的特定属性。因此，以原子的电子结构为首要标准的周期表与以某些化学或物理性质为主要标准的周期表是不同的。

These versions don’t differ by much, but there are certain elements – hydrogen for example – which one might place quite differently according to the particular property one wishes to highlight. Some tables place hydrogen in group 1 whereas in others it sits at the top of group 17; some tables even have it in a group on its own.

这些版本差别不大，但有一些元素——比如氢——根据人们想要强调的特定性质，它们的位置可能会有很大的不同。有些表格把氢放在第一组，而另一些则放在第17组的顶部;有些表甚至把它单独放在一个组中。

Rather more radically¹⁰, however, we can also consider ordering the elements in a very different way, one which does not involve atomic number or reflect electronic structure – reverting¹¹ to a one-dimensional list.

然而，更根本的是，我们还可以考虑以一种非常不同的方式对元素进行排序，一种不涉及原子序数或反映电子结构的排序——恢复到一维列表。

The latest attempt to order elements in this manner was recently published in the Journal of Physical Chemistry by scientists Zahed Allahyari and Artem Oganov. Their approach, building on the earlier work of others, is to assign to each element what’s called a Mendeleev Number (MN). There are several ways to derive⁵ such numbers, but the latest study uses a combination of two fundamental quantities which can be measured directly: an element’s atomic radius¹² and a property called electronegativity which describes how strongly an atom attracts electrons to itself.

科学家Zahed Allahyari和Artem Oganov最近在《物理化学杂志》上发表了用这种方式排列元素的最新尝试。他们的方法是在其他人早期工作的基础上，给每个元素分配所谓的门捷列夫数(MN)。有几种方法可以得出这样的数字，但最新的研究使用了两个可以直接测量的基本量的组合:元素的原子半径和一种称为电负性的特性，该特性描述了原子吸引电子的强度。

If one orders the elements by their MN, nearest neighbours have, unsurprisingly, rather similar MNs. But of more use is to take this one step further and construct a two-dimensional grid¹³ based on the MN of the constituent¹⁴ elements in so called “binary¹⁵ compounds”. These are compounds composed of two elements, such as sodium chloride, NaCl.

如果我们按元素的MN来排序，那么最邻近的元素的MN也会非常相似。但更有用的是更进一步，以所谓的“二元化合物”中组成元素的MN为基础构建一个二维网格。这些化合物由两种元素组成，如氯化钠(NaCl)。

What is the benefit of this approach? Importantly, it can help to predict the properties of binary compounds that haven’t been made yet. This is useful in the search for new materials that are likely be needed for both future and existing technologies. In time, no doubt, this will be extended to compounds with more than two elemental components¹⁶.

这种方法的好处是什么?重要的是，它可以帮助预测尚未生成的二元化合物的性质。这对于寻找未来和现有技术可能需要的新材料是很有用的。毫无疑问，随着时间的推移，这种方法将扩展到含有两种以上元素的化合物。

A good example of the importance of the search for new materials can be appreciated by considering the periodic table shown in the figure below. This table illustrates¹⁷ not only the relative abundance of the elements (the larger the box for each element, the more of it there is) but also highlights potential supply issues relevant to technologies that have become ubiquitous and essential in our daily lives.

一个关于寻找新材料的重要性的好例子可以通过考虑下表中所示的元素周期表来理解。这个表格不仅说明了元素的相对丰度(每个元素的盒子越大，它就越多)，而且还强调了与我们日常生活中无处不在和必不可少的技术相关的潜在供应问题。

Take mobile phones, for instance. All of the elements used in their manufacture are identified with the phone icon¹⁸ and you can see that several required elements are becoming scarce – their future supply is uncertain. If we are to develop replacement¹⁹ materials which avoid the use of certain elements, the insights gained from ordering elements by their MN may prove valuable in that search.

以手机为例。所有在制造过程中使用的元素都用手机图标标识，你可以看到一些必需的元素正在变得稀缺——它们的未来供应是不确定的。如果我们要开发避免使用某些元素的替代材料，那么根据元素的MN排序所获得的洞见可能在这一探索中被证明是有价值的。

After 150 years, we can see that periodic tables are not just a vital educational tool, they remain useful for researchers in their quest for essential new materials. But we should not think of new versions as replacements²⁰ for earlier depictions. Having many different tables and lists only serves to deepen our understanding of how elements behave.

150年后，我们可以看到，元素周期表不仅是一种重要的教育工具，在研究人员寻找重要新材料的过程中，它们仍然很有用。但我们不应该认为新版本是早期描述的替代品。拥有许多不同的表和列表只能加深我们对元素行为方式的理解。