That the nobility of man, acquired in a hundred centuries of trial and error, lay in making himself the conquerer of matter, and that I had enrolled in chemistry because I wanted to remain faithful to this nobility. That conquering matter is to understand it, and understanding matter is necessary to understanding the universe and ourselves: and that therefore Mendeleev’s Periodic Table, which just during those weeks we were laboriously learning to unravel, was poetry, loftier and more solemn than all the poetry we had swallowed down in liceo; and come to think of it, it even rhymed!

Primo Levi, The Periodic Table.

This year marks the 150th anniversary of the periodic table of the elements (TPE) which currently has 118 entries, the latest arrival (the Tennessine) was discovered 10 years ago (2009), and I feel obliged as a chemist to give some a small informative contribution to celebrate this important event.

On March 6, 1869, the Russian chemist Dmitri Ivanovich Mendeleyev presented to the Russian chemistry society, a communication entitled “The dependence of the properties of the chemical elements on atomic weight.” In this historical communication, Mendeleev presented a new way to organize the known chemical elements in the form of a table that evidence their periodic propriety. This table established the fame of the author as it was the first version of the modern periodic table of chemical elements.

Mendeleyev, while preparing the second edition of his chemistry book, was looking for a way to classify the chemical elements then known (53 or less than half of those we know today) based on their properties. As Mendeleyev told later, the inspiration came to him in a dream (it is not the first time that Orfeo suggests chemists their great scientific discoveries!) [2]:The periodic table of Mendeleev elements. The dashes represent unknown elements in the year 1871. (source of the figure: Wikipedia)Mendeleyev, while preparing the second edition of his chemistry book, was looking for a way to classify the chemical elements then known (53 or less than half of those we know today) based on their properties. As Mendeleyev told later, the inspiration came to him in a dream (it is not the first time that Orfeo suggests chemists their great scientific discoveries!) [2]:

“In the dream, he saw a table where all the elements fell into place as required. Awakening, he immediately wrote the fancied table down on a piece of paper.”

More likely as results of brilliant chemical intuition, Mendeleev had discovered the way to order the elements to highlight the surprising periodicity in their chemical properties. In fact, if the chemical elements are arranged in groups of the same valence and then sorted with increasing atomic mass, they will organize along the columns of a periodic table.

On the basis of this periodic organization, Mendeleev was able to predict the existence of several chemical elements not yet isolated in their pure state, such as, for example, Germanium (initially called by Mendeleev ekaalyuminiy, which in Russian means “analogous (eka) to Alluminium”), Gallium (eka-silicon,” analogous (eka) to Silicon”) and lo Scandium (ekabor,” analogous (eka) to Boron”). A few years later, these elements were discovered and isolated. In fact, Germanium was discovered by C. A. Winkler in February 1886 Winkler in the argyrodite mineral. In 1875, P. E. L. de Boisbaudran succeeded in isolating Gallium with electrochemical methods. Finally, the Scandium was isolated in 1879 by F. Nilson from an impure sample of Ytterbium. The chemical properties of the new elements turned out to be surprisingly identical to those predicted by Mendeleev. This enormous success definitely gave history the name of this unknown Russian chemist and his table of chemical elements.

In 1955, the artificial element 101, prepared by the bombardment of the einsteinium with helium by A. Ghiorso, G. Harvey, R. Choppin, SG Thompson and GT Seaborg at the Berkeley Radiation Laboratory in the USA, was called Mendelevium in honour of Mendeleyev.

In the following graph of recurrence in Figure 1 the temporal differences between the discovery of new chemical elements are shown. The chart shows that year gap in the discovery of a new chemical element was quite small, arriving in some periods to the breakthrough of two or three chemical elements per year.

Curious observations on the names and symbols of the elements

On the frequency of letters in chemical symbols. The histogram in Figure 2 represents the abundance of the letters present in chemical symbols. The most represented letter is C followed on an equal footing by the letters N, P, S, T.

The median length of the English chemical element names is eight (see Figure 3). A tendency to increase with atomic weight is observed. Furthermore, it is interesting to note that there are regular fluctuations with groups of contiguous elements that show oscillations about the linear trend.

In Figure 4, in honour of Mendeleev, the statistic for the names of the chemical elements in Cyrillic characters is also reported. In this case, the median length is equal to seven. Also, in this case, we observe the same tendency to a slight increase of the names length with the atomic number.

The Mendeleyev’s Dream: An educational game in awk

For the anniversary of 150 years of the Periodic Table, I brushed up an program that I made long ago and that, in honour of Mendeleyev, I have called “The Mendeleev’s Dream”. The program (the listing of the program is available in the Appendix of the Italian language version of the article) is a simple educational game written in the awk language that can help, while having fun, to memorize the elements in the table. The program contains three games that aims to guessing the elements on the periodic table based on three types of question games with multiple choices. The game has a score, with a minimum of zero and a maximum of 118. The initial score is set to 59. By changing the variable lang it is possible to select the language used to indicate the name of the elements. (0: English, 1: Italian, 2: German).

Game 1

In this game, you need to guess the name of the element in the position indicated by the red cross. 5 possible symbols or element names are suggested. 5 attempts are allowed, each negative answer is penalized by 0.1 points after 5 attempts the answer is given with a total penalty equal to -0.5.

Game 2

The second game aims to guess the position of a randomly chosen element, given its symbol or its name. 5 possible locations are suggested in the periodic table numbered from 1 to 5. 5 attempts are allowed, each negative answer is penalized by 0.1 points after 5 attempts the answer is given with a total penalty equal to -0.5.

Game 3

In this game, you need to guess the name of the element indicated with an X in the periodic table. The program suggests the letters contained in the name with dashes. 5 attempts are available if the proposed name is not correct, the characters that coincide with those of the exact name are reported in the suggestion. After 5 attempts, the correct answer is given, but with a total penalty of -0.5.

REFERENCES

Many books have been written on the periodic table of the elements, its history and those of its elements. In the following list, I report the reference to articles cited in the blog and to some books on the subject that I recommend to read.

1.Mendeleev, D. “The natural system of elements and its application to the indication of the properties of undiscovered elements”. Journal of the Russian Chemical Society (in Russian). 3: 25–56, (1871).

2. Paul Strathern. Mendeleyev’s Dream: The Quest for the Elements. Penguin, (2001).

3. Primo Levi. The Periodic Table.  Penguin Classics, (2000).

4. John Emsley. The Elements of Murder: A History of Poison. Oxford University Press, (2006).

5. John Emsley. Nature’s Building Blocks: An A-Z Guide to the Elements. OUP Oxford, (2011).

6. Hugh Aldersey-Williams. Periodic Tales: The Curious Lives of the Elements. Penguin, (2012).

7. Nick Mann and Theodore Gray. The Elements: A Visual Exploration of Every Known Atom in the Universe. Black Dog & Leventhal, (2011).

8. Vari. The Periodic Table Book: A Visual Encyclopedia of the Elements. DK, (2017).