The Periodic Table and the Four New Elements

Was rummaging through my files on the computer, when I came upon this piece. It was written for ChemMag, the annual journal of the Department of Chemistry, Women’s Christian College, Chennai. It appeared in print in the 2016 issue.

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The year 1869 was momentous for Chemistry. It was the year when Dmitri Mendeleev published the first ever Periodic Table [1]. But then, discoveries in science do not occur in vacuum (unless your protocol calls for vacuum, i.e.). Mendeleev gave us the Periodic Table, but he was drawing on work already done by Antoine Lavoisier, Johann Döbereiner, John Newlands and several others.

Historians of Chemistry believe that one fine night in 1869, Mendeleev literally fell asleep on his desk atop some note cards. Each of these cards carried information on every element known at that point. Mendeleev had 65 cards to work with. When Mendeleev awoke, he knew exactly how these cards were to be arranged, and he set about arranging these 65 cards in a systematic order based on atomic weights, which eventually gave us Mendeleev’s Periodic Table [2].

That was 1869. And this is 2016. From 65 elements then, our periodic table now boasts of 118 elements. We know that the elements in the Modern Periodic Table are arranged in increasing order of atomic numbers. We have the Groups – the vertical columns – which house elements based on their similarities in chemical properties, due to the same number of electrons in the outermost shell. And we have the Periods – the horizontal rows – which have elements arranged in the order of increasing atomic number, signifying an increase in the number of outer electrons, thereby demonstrating a move from metallic to non-metallic characteristics of the elements.

As new elements were discovered, they were provided appropriate places in the Periodic Table depending on their similarities with elements already known. But perhaps the genius of Mendeleev is in the predictive power of his Periodic Table. (That said, opinion however divides on whether it was Mendeleev or Newlands, who first left empty spaces for undiscovered elements.)

As the world was getting ready to ring in the new year, on 30 December, 2015, the International Union of Pure and Applied Chemistry (IUPAC) announced that they had confirmed the existence of elements 113, 115, 117 and 118. This meant that the hitherto incomplete seventh row of the Periodic Table was now complete [3].

All of these four elements are highly unstable superheavy elements with very short lifetimes, and are synthesised by bombarding heavy metals with ionising radiation.

Element 113 – with a placeholder name of ununtrium – was synthesised at the RIKEN Nishina Center for Accelerator-based Science in Japan. The lab lead by Kosuke Morita had been trying to synthesise this element since 2004 with varying degrees of success.

Elements 115 (ununpentium), 117 (ununseptium) and 118 (ununoctium) were synthesised by particle accelerator scientists from the US and Russia.

With the elements synthesised, now comes the rather interesting task of naming them. Like astronomers discovering cosmic bodies, scientists discovering elements also get the right to name them. It has been suggested elemental names can be based on mythological concepts, places, famous scientists etc. (Polonium, Einsteinium – ring a bell?) In line with this thought, element 113 discovered by the Japanese scientists may well be named Nipponium. Deliberations are on regarding the naming of the other three elements.

In theory, the Periodic Table could still get bigger. We’ll have to wait and watch. Or contribute, and watch. But amidst this scientific celebration, there remains a rather comic situation that calls for our attention: Education Boards all over the world need to update their Chemistry textbooks which have now been rendered obsolete due to these discoveries!

References:
[1] On the Relationship of the Properties of the Elements to their Atomic Weights, D. Mendelejeff, Zeitschrift für Chemie 12, 405-406 (1869).
[2] http://time.com/4165979/periodic-table-new-elements/
[3] http://www.iupac.org/news/news-detail/article/discovery-and-assignment-of-elements-with-atomic-numbers-113-115-117-and-118.html

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Philosopher’s Wool and a Walk Down Chemistry Lane

Zinc oxide is philosopher’s wool. It is formed when zinc burns in air. The white fumes that form as a result of this burning produce a wool like substance, earning it the epithet – philosopher’s wool.

I went on Google Books to find some early references of the oxide, and what I found thrilled me.

The first is a treatise titled Chemical Instructor: Presenting a Familiar Method of Teaching the Chemical Principles and Operations of the Most Practical Utility to Farmers, Mechanics, Housekeepers and Physicians and Most Interesting to Clergymen and Lawyers. Intended for Schools and Popular Class-room by Amos Eaton. This was published in 1822. Eaton famously co-founded the Rensselaer School for ‘the application of science to the common purposes of life’ and was an advocate for the inclusion of women in science.

The following is an image from his treatise on Google Books describing the classroom demonstration of the preparation of philosopher’s wool.

 

And the following are two rather telling highlights from the Preface of the same treatise.

Here’s another book titled Chemical experiments : illustrating the theory, practice, and application of the science of chemistry, and containing the properties, uses, manufacture, purification, and analysis of all inorganic substances : with numerous engravings of apparatus, etc. by G. Francis. This was published in 1842.

The very first paragraph of the Preface here reads:

The Chemist and Druggist will find in this small book the best method of manufacturing every chemical substance which he is likely to want. The Lecturer will recognize the most remarkable properties of them all, clearly pointed out by such experiments as are easy and striking. The Student will be able to refer to and to repeat the experiments of the classroom with facility. The Manufacturer will find the economical principles of his trade illustrated and the best receipts for his articles given. While he who seeks amusement only will have a wide field before him, from which he may cull the choicest flowers; and should his means be limited, or his residence remote from cities, still little impediment will arise on this account, as one portion of the book assists the other; one experiment explains the manufacture of that substance of which other experiments explain the nature.

Sample this first page from the Introduction chapter which talks of chemistry in those days, which was a part of Natural Philosophy.

And here’s the combustion of zinc described in the form of a laboratory experiment rather than as a demonstration in the previous treatise.

Reading such texts, how can one miss the romantic appeal of chemistry? I hope more and more chemistry (science) educators take it upon themselves to incorporate such examples from the history of chemistry (science) to enthuse students towards the subject, and to inculcate in them an understanding and appreciation of the development of the subject.

PS. Here’s a poem by Brian Culhane titled Philosopher’s Wool from Able Muse, Winter 2009 issue.

Images from Google Books and archive.org