Dr Eric Scerri is a leading chemist and philosopher of science, specialising in the history of the periodic table. He has several published books, including “The Periodic Table: Its Story and Its Significance” (OUP, 2007) and “A Very Short Introduction to the Periodic Table” (OUP, 2011).
Dr Scerri, welcome to The Chemical Blog. Can you tell us about your current position?
I’m a chemistry lecturer at the University of California, Los Angeles. I teach general chemistry classes up to 350 students. I also teach classes in the history and philosophy of science to smaller groups of students and do research in the history and philosophy of chemistry.
Going back in time, do you remember when you decided to become a chemist? What motivated you to follow that field?
I became interested in high school while in London. In one of my books, I tell the story that I was fooling around in the back of the class one day, when my chemistry teacher, Mrs Davies, spotted me and made me sit at the front, the way teachers use to do in those days. I did and I began to see that chemistry was actually quite interesting and started reading up on my own and began to get a grip on the subject.
You’ve been classed as a pioneer in history and philosophy of chemistry. How did this area develop in combination with your work in chemistry?
Well, I’ve always had a foot in both camps, and I was equally interested in sciences and humanities. In fact, it was a difficult decision in high school. We had to choose sciences or humanities for A levels. I chose chemistry, physics and mathematics. However, as a result I was no longer doing subjects I really liked, such as history or English. But that urge always continued with me and later I started seeing that I could combine both interests.
Do you find it easy to combine both subjects? How do keep a foot in the history and philosophy of chemistry as well as the chemistry fields?
I wouldn’t say it’s easy, but it’s rewarding. You have to follow what you’re interested in and your inclinations. It’s not particularly easy, and sometimes colleagues or even students wonder why I start to discuss some historical points in the middle of the lecture. For them, it may not be quite so important, but I regarded it as being essential allowing students to get a deeper insight into the ways concepts and theories develop.
This information is not something one gets from usual text-book accounts
I suppose it helps us understand the background to some of the discoveries and how society worked at the time.
It helps to understand that science is a human endeavour, and that it involves personalities. There were struggles, dead-ends and so on. This information is not something one gets from usual text-book accounts. Books tend to present results as cut and dried which is far from the truth.
Maybe if books revealed more about the human side, it would get more students interested in sciences, instead of the straightforward approach they have now. Moving on to the periodic table, it seems to be a favourite subject of yours. How did that love affair started? Why are you so passionate about it?
Again, it started in high school. After being exposed to a certain amount of chemistry and finding it quite complicated, we were then presented with the periodic table and things seemed to fall into place. It’s this wonderful organising scheme that just makes sense of everything. In addition, I also like classification and I like the visual aspects of the periodic table. I like the fact that it combines physics and chemistry and history of science and philosophy of science.
It has many levels to it and it’s just one unified chart. There’s a fantastic diversity in the elements, all with unique and with quite different properties, and yet there’s this one big connection. They’re all part of a grand scheme and that grand scheme is the periodic table.
Chemists have a little bit of an inferiority complex, feeling they just stir around in pots and pans and solutions, while physicists are the really clever ones who see things theoretically and come along and explain everything
You’ve mentioned several times the link between chemistry and physics. How do you explain your previous comments about physics “invading” chemistry?
At around the turn of the 20th century many discoveries were made such as x-rays, radioactivity, the electron, and soon afterwards the structure of the atom began to be understood. Of course, this had an effect on chemistry and our understanding of the periodic table.
I use the word “invading” almost in a deliberate way. There’s a sort of uneasy situation that exists between chemists and physicists, whereby the deep explanations are supposed to reside in physics. Physics is usually thought to be able to explain everything in chemistry. Chemists have a little bit of an inferiority complex, feeling they just stir around in pots and pans and solutions, while physicists are the really clever ones who see things theoretically and come along and explain everything. This question has implications for chemical education. A lot of my work has been an examination of to what extent is it really true that physics explains everything in chemistry. It does to a great extent, but it doesn’t completely or there would be no need for chemistry.
So, is chemistry going to disappear over the next century? Or will there be a place for chemistry in the future?
I don’t think it will, because even if we have a deep theoretical understanding, there is no substitute for people who are actually operating on a chemical level and doing experiments and discovering new molecules and so on. You can’t always anticipate what going to happen.
Chemistry is not being replaced, but there’s an interesting philosophical paradox, a puzzle about the relationship between different fields of science. It’s not just chemistry and physics, but for example biology and chemistry. How much of biology is explained by chemistry, and again the answer is a lot of it is. To a large extent, biology is nothing but chemistry, and yet there seems to be something that exists on a biological level that is not reducible.
Hydrogen sits a little bit uneasily at the top of group 1. For example, it is not a metal like the other elements there…
You’ve suggested some revisions to the periodic table in particular to hydrogen’s location. Can you explain why do you think hydrogen is in the “wrong place” or why is there a better place for it?
Hydrogen sits a little bit uneasily at the top of group 1. For example, it is not a metal like the other elements there. The other elements are solids that can be cut with a knife, but hydrogen is a gas. It’s rather unlike the other elements, physically at least. Of course it does have some chemical similarities. It forms a +1 ion and this is one of the reasons it’s always been placed in that group.
I started looking at the concept of triads, which is one of the places historically where the periodic table began. This was one of the contributing ideas, and even before there was a periodic table, groups of three elements were identified, where the middle element has the average atomic weight between the element above and below. I tried to do that not with atomic weight, but atomic number, which provides a more correct ordering of the elements.
If you try to do that, you’ll find that hydrogen is currently not a member of a triad. On the other hand, about 50 % of all possible triads in the periodic table are perfect triads using atomic number. So, I had the idea of moving hydrogen on top of group 17 (halogens) noticing that it creates a new triad. Other people have suggested moving hydrogen to that group for chemical reasons, such as the fact that it forms a -1 ion, as do those elements, but I think I’m the first person to suggest moving it there because it creates a new atomic number triad.
Helium is usually placed in group 18, but some argue it should be placed in group 2 of the periodic table. It’s nice to see that these ideas are being increasingly debated
You’ve criticised some artificial triads, created just for the sake of creating triads. Could this another example?
The answer is yes. I’m putting the suggestion out for discussion. I don’t think there’s enough discussion on the periodic table and even chemists take the periodic table for granted and don’t ask themselves these more philosophical questions about whether there is an optimal periodic table. You may hear “I don’t care whether hydrogen is in group 1 or 17, or even on its own, hovering about around the periodic table”. I find that surprising and for me that’s an unacceptable answer. I believe every element has a correct place and it’s a matter of discovering where that place is. By making this proposal, I’m partly trying to shake things up and get people thinking about the optimal periodic table.
There’s also a parallel discussion about the position of helium. Helium is usually placed in group 18, but some argue it should be placed in group 2 of the periodic table. It’s nice to see that these ideas are being increasingly debated. With the growth of philosophy and chemistry, it seems that there is now more space for such discussion these days.
We should look at the periodic table as moving and evolving, rather than static. You’ve mentioned in your books about an ideal table. You do think there is an ideal table? Maybe 3D? Is there something we haven’t discovered yet that could be a better way to present the periodic table?
There are 3-dimensional periodic tables, but I don’t think they add anything fundamental to the periodic table. The whole point about periodicity, is that as you’re walking through the table, every now and then there’s a repetition, which can be represented very well in a 2-dimensional table. 3D tables bring in the possibility of secondary relationships. That is a very interesting area and recently I’ve been focusing on that and maybe using a third dimension can highlight further aspects. But these aspects can be highlighted equally well on a pyramidal periodic table, and that’s a 2-dimensional table. I have to come back and say that I don’t really think 3D is going to help.
But you do believe there is a perfect periodic table, but we just haven’t found it yet?
Yes, I do believe that.
Finally, with regards to new projects you’re working on, any further books on the periodic table? Any other projects?
I just finished a book that’s coming out in a couple of months called “A tale of seven elements”, which examines the 7 elements that were still missing when atomic number was discovered. After atomic number was discovered, it was realised that between the old limits of the periodic table, or between element 1 and 92, there were just 7 gaps remaining to be filled. Before that, it was ambiguous and there could have been fewer or more elements. The discovery of the atomic number had the effect of stepping-up the programme for the discovery of these 7 elements. Having said that, it was not a straightforward path, there many twists and turns and many interesting human stories of people claiming to having discovered certain elements and others refuting the claims.
That project is now done, and the next one I’m thinking of doing is a popular book on quantum mechanics. I’m often trying to explain basic ideas in quantum mechanics to my students. I’d like to take it further and explain quantum concepts to a general public.
In an odd sort of way, chemists use quantum mechanics in education more than physicists. I’m explaining basic ideas in quantum mechanics almost on a daily basis when I’m teaching chemistry. I think it might give me angle on how to explain it to a general audience. The story is fascinating. There are hundreds of books on the subject, but I believe there is still room to explain this theory better. It is after all the most important successful and influential theory that exists at the moment. In a sense, it explains everything.
Thank you for your time and I’m looking forward to reading your new books.