Periodic Table Of The Elements Turns 150
Maybe you've felt a certain chemistry with 2019 but don't know why? Maybe it's because this year marks the 150th anniversary of the Periodic Table of the Elements. It's considered the founding document of modern chemistry, one you may have studied in school.
UW-Madison professor of chemistry Bassam Shakhashiri knows both the history of the table, and its modern relevance. He says the table came about through a collaboration of a few scientists but that Dmitri Mendeleev properly gets much of the credit.
"Dimitri Mendeleev, the Russian chemist, he proposed — sometimes people say he discovered — the pattern of similar behavior [of certain elements] and arranged them," Shakhashiri explains.
On modern relevance, and how uses of the elements change, Shakhashiri cites lithium (symbol Li), in the table: "Lithium batteries are very useful to us. Lithium is also used in the medical profession, for a variety of things."
Shakhashiri also notes how lead (symbol Pb) has a less popular image than in Mendeleev's day. Nowadays, lead is often viewed as a contaminant in soil and water.
Read the full transcript of WUWM's Chuck Quirmbach and Bassam Shakhashiri's conversation here:
Bassam Shakhashiri: Mendeleev the Russian chemist was teaching a course and he was writing his lecture notes and tried to write an inorganic chemistry book about chemical behavior of substances. And it came to him that there possibly is a pattern of repeated resemblance of behavior of certain elements. And so that's what he did. He proposed, sometimes, you know, people say he discovered the pattern of similar behavior and arranged the elements, according to are their atomic weights. Later on, this turned out to be not so correct, but that's how it is in science. We learn the periodic table as the elements arranged according to the atomic number, which is an integer, a whole number. That's the number of protons in an atom of that element. So they range from one, which is element hydrogen, all the way to element 118 which is the total number of elements in the periodic table today,
Chuck Quirmbach: Was he creating this and and the others that can certainly contributed to it, were they trying to serve some industry like cannon makers?
Shakhashiri: Human beings all of us are naturally curious. We ask questions, all kinds of questions. You know, why is the sky blue? We make observations and try to make sense out of these observations and that's what science is all about. It's about examining behavior, natural behavior, and trying to describe in words and language and in symbols, what the behavior pattern might be. So it's really as a result of curiosity. It was not to serve any other purpose, but curiosity leads to discovery and discovery leads to application.
Quirmbach: What sort of applications took off?
Shakhashiri: Fabulous applications. When the elements were arranged in this chart in the periodic table, it was easy to see right away that there are missing elements that have not been discovered yet, that have not been identified. So the search was on to find them and to identify them and to characterize them. So that was a very, very important consequence of putting the elements in this organized fashion that we call the periodic table. Later on when we got to the so called heavy elements, to the elements that have 92 protons or more, uranium, for example. Then, as people started theorizing, making suggestions, scientists were saying, maybe we can synthesize elements we can make new elements and The transuranium elements were synthesized by several people. One group at University of California, Berkeley, led by the scientist, Glenn Seaborg, proceeded to make new elements. And Glenn Seaborg proposed that maybe there should be more elements that we don't know about and other scientists, not only in the United States, but in Russia and elsewhere, undertook serious experimentation that led to identifying some of these synthetic elements. They weren't really discovered. They were made, they were synthesized and, interestingly enough, some of these heavy elements do not have a long lifetime, they disintegrate, they released energy, and disintegrate. They've got very stable, some are their lifetime is in the order of seconds. And that's another consequence of these discoveries and how to develop the technology to detect these transformations that are made, so there is this is just very, very intriguing and very rewarding pursuit. As you can imagine, it's also very challenging, but that's where the reward, rewarding aspect comes in.
Quirmbach: And remind me the synthetic elements they’re on the table too, aren’t they?
Shakhashiri: They’re on the table, elements in the last row that you see at the bottom of the table. They're made by groups of scientists, men and women. And that's another aspect that I want to include in this conversation. How these elements are named. Originally, the elements were named, many of them, most of them, after the location, the region where they were isolated and discovered, but with the new synthetic elements, that credit is given to the people who have first identify it. And then there's a lot of verification that goes on. There is an international group. It's called the International Union of Pure and Applied Chemistry. This organization has the final say about the naming of an element a group says they have discovered, again, I use the word discovered advisedly, here they synthesize. But who knows, maybe in the universe, some of these elements are there too, but their lifetime is very short. But the International Union of Pure and Applied Chemistry then, after very careful scrutiny, decides finally on the name of the elements, and of course, strength in the periodic table, according to its own atomic number.
Quirmbach: Would you argue this table is still useful today by not just teachers and classrooms?
Shakhashiri: Of course, it's useful and sometimes the teachers in the classroom don't use it the way it should be used. It's not just a memorize the names and symbols of these elements. It's the Think about the patterns of behavior and the way in which the chemical and physical properties of the different substances that we encounter are related to each other. I know in many classrooms if people say memorize, I used to say in my classroom memorize the names and symbols of the first 36 elements in the periodic table, the first assignment in my freshman chemistry courses UW-Madison, and students would say, well, why do I have to memorize and I said, because when you talk about the element potassium, you should know that it's represented by the symbol K, not by the symbol P, the symbol P refers to phosphorus. So there are ways by which the periodic table as an organized means of chemical behavior can be used instructively to make students aware of the beauty of it. That's what I advocate, not only in my own teaching but in workshops that I do with teachers with good with others and, and with the public at large. So the periodic chart of the elements, the periodic table of the elements can be put to good use much, much more importantly than memorizing the names and symbols, but knowing what they stand for, is the identity of the element. Why is potassium’s symbols K? Why are the elements arranged in columns in the periodic table? What is the pattern of behavior? How is it correlated to the structure of the electrons outside the nucleus? All kinds of beautiful manifestation can be discerned and used properly.
Quirmbach: Let's explore that example just a little bit more about K and potassium, is it more related vertically to sodium above it or to calcium to the right of it? In other words, are the groupings more vertically or horizontally or a bit of both?
Shakhashiri: There are correlations all over the place. That's a very good question Chuck. The pattern I was referring to is the vertical pattern. The chemical properties of lithium, and sodium, and potassium, and rubidium, and cesium compounds are very similar to each other. There is periodic repetition. This is why it's called periodic table if there's periodicity in the relationship between potassium and calcium, which is right next to it that's on the horizontal line. What's on the horizontal line is going across the periodic table, where the number of electrons begins to increase as you go from left to right at the table. And you can see that because the atomic number is different, the atomic number goes up. So the number of electrons has to go up. So the beauty of the periodic table is that the elements that are in columns, up and down, have similar properties. But there are similarities within a group going across too.
Quirmbach: Do you ever think about how the images or the popular images of some of these elements have changed over the years. I'm thinking that for example, lead and phosphorus these days, often seen as pollutants in water and other places. Lithium, which, as a kid I didn't know too much about now we hear about a lot of lithium used in batteries. Is that the good way to look at this table that had the elements change and use and image a lot?
Shakhashiri: Well, our own awareness changes and that's again going back to what happens in the classroom and what happens also in popularizing the understanding of science. So, lithium batteries are very useful to us. Lithium is also used in the medical profession for you know, a variety of purposes. Lead on my website, saifan.org, I have a one page description of the properties of lead. Lead is an insidious substance. So understanding the properties and the usefulness and the hazards is a very important part of what we do in science and what we do in society. So it's very important that we ask the question, why was the left foot in the gasoline in the first place? It was to improve the knocking that the engines were having it was an anti-knock additive. But then we discovered that it has very bad environmental consequences and health consequences. So the slogan was was take the lead out and have other substitutes in there. The periodic tables can be put to a lot of good usage. And it's fascinating for all of us to ask the kinds of questions that you're asking here.
Quirmbach: Well, nearly my final question is we're at 118 right now. Are you aware that there might be more added other people trying to synthesize more Are they all going to be synthetic or the will there be so-called natural ones added?
Shakhashiri: Well, that was one of the predictions that Glenn Seaborg and his group made and others to is not just one individual. that there may be another set, another series of elements, which atomic number is very, very large, maybe, you know, going all the way to 137, maybe even higher than that, that would be stable, but haven't been discovered yet, and have not been synthesized yet. That's something for all of us to think about and to enable scientists who are specialists in these areas, and give them the support, to contemplate and devise experiments, methods and technologies to explore the beautiful complex world that we live in.
Quirmbach: Because that between 118 and 137, might be something that's very valuable, cures a lot of problems, your hope?
Shakhashiri: Who knows, that's why we do experiments to satisfy our curiosity and when we may discoveries, it is my sincere hope and wish that we put these discoveries to good use. Once you discover something, you have to make a judgment about putting it to good use and it's my hope and sincere wish that all scientific technological discoveries are put to good use.
Support is provided by Dr. Lawrence and Mrs. Hannah Goodman for Innovation reporting.
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