The Periodic Table of the Elements (Encore)

Summary

Everything Everywhere Daily Podcast Summary

Episode: The Periodic Table of the Elements (Encore)
Release Date: January 2, 2025
Host: Gary Arndt | Glassbox Media

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Introduction to the Periodic Table

In this encore episode of Everything Everywhere Daily, host Gary Arndt delves deep into the history, significance, and structure of the periodic table of elements. He explores how this fundamental tool revolutionized our understanding of the natural world and continues to be a cornerstone in various scientific disciplines.

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Early Discoveries and Initial Classifications

Gary begins by tracing the origins of elemental discovery, highlighting how early humans identified metals such as copper, lead, iron, silver, and gold. Although ancient civilizations recognized these materials, they lacked the conceptual framework to understand elements at an atomic level.

“The very first elements were discovered by early humans... they knew that one thing like copper was different from another thing like iron.” (02:10)

By the late 18th century, with the advent of modern chemistry, the number of recognized elements had expanded to over two dozen. French chemist Antoine Lavoisier made a significant stride by attempting to catalog these elements systematically in 1789. Despite including non-elements like light and heat, Lavoisier correctly defined an element as a substance that cannot be broken down further.

“He defined an element as something which could not be broken down any further. Today we call them atoms.” (03:15)

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Progress in the 19th Century: Towards a Pattern

As chemistry advanced in the 19th century, numerous new elements were discovered, particularly rare ones. German chemist Johann Wolfgang Döbereiner identified triads—groups of three elements with similar properties and sequential atomic weights—in 1829, hinting at an underlying order.

“Döbereiner noticed that many of the elements that displayed similar properties could be grouped into threes.” (04:05)

French geologist Alexandre Milbré de Cinquechais further pushed the boundaries by proposing a helical organization of elements based on periodicity, though it lacked the practicality needed for widespread adoption.

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Mendeleev’s Revolutionary Periodic Table

The pivotal moment in the organization of elements came in 1869 with Dmitri Mendeleev, a Russian chemist, who published his version of the periodic table. Unlike his predecessors, Mendeleev arranged elements in rows and columns based on atomic weight, leaving deliberate gaps for yet-to-be-discovered elements. This bold move not only accommodated known elements but also predicted the existence and properties of undiscovered ones.

“The big breakthrough in the organization of the elements came from a Russian chemist named Dmitri Mendeleev.” (05:30)

Mendeleev's table initially listed 63 elements, grouped primarily into metals and nonmetals. Despite some inaccuracies, such as the placement of certain elements, his periodic table gained credibility when his predictions about new elements were validated by subsequent discoveries.

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Advancements in Atomic Theory and the Periodic Table

The discovery of the atomic nucleus by Ernest Rutherford in 1911 provided a solid foundation for understanding the periodic table's structure. This breakthrough suggested that elements should be arranged according to atomic number (the number of protons) rather than atomic weight, a realization that further refined the table’s accuracy.

“After Rutherford discovered the nucleus, it was suggested that the chart followed the atomic number of the atom... which is what ultimately made the table almost a perfect fit.” (06:45)

Physicist Henry Moseley, in 1913, used X-ray spectroscopy to confirm that atomic numbers, not atomic weights, determined element placement. His work resolved discrepancies in Mendeleev's table and confirmed the existence of elements between aluminum and gold, which were later discovered as predicted.

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The Structure of the Modern Periodic Table

Gary meticulously explains how the modern periodic table is organized:

• Periods: Each horizontal row represents a period corresponding to the number of electron shells an element possesses. For example, the first period contains only two elements, hydrogen and helium, due to the limited capacity of the first electron shell.

• Groups: Each vertical column, or group, categorizes elements based on the number of electrons in their outermost shell. Groups share similar chemical properties. For instance:

  • Group 1: Alkali metals (e.g., lithium, sodium, potassium) are highly reactive with one electron in their outer shell.
  • Group 18: Noble gases (e.g., helium, neon, argon) are inert due to their full outer electron shells.

“Each column is known as a group. The group reflects the number of electrons in the upper electron shell.” (08:20)

The periodic table also features the rare earth elements, or lanthanides and actinides, typically displayed separately to maintain the table’s readability.

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Discovery of Synthetic Elements and Future Prospects

While uranium (atomic number 92) was the last naturally occurring element discovered in 1939, the quest for superheavy elements extended beyond. Through nuclear reactions and the fusion of large atoms, scientists have synthesized elements up to oganesson (element 118).

“The last element on the periodic table is element 118, called Oganesson, and it falls in the same column as the noble gases.” (08:55)

However, these synthetic elements have extremely short half-lives, existing only fractions of a second before decaying. The possibility of discovering stable superheavy elements remains an open question, captivating researchers and maintaining the periodic table's dynamic nature.

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The Beauty and Utility of the Periodic Table

Gary concludes by emphasizing the periodic table's elegance and practicality. It not only serves as an essential educational tool but also stands as a masterpiece of scientific organization, reflecting the intrinsic relationships between the elements that compose our universe.

“The periodic table is really an amazing thing. It so neatly and cleanly encapsulates how all the elements which make up the world relate to each other. It isn't just a handy educational aid, but it also should be considered an actual thing of beauty.” (09:40)

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Conclusion

In this comprehensive episode, Gary Arndt successfully unpacks the intricate history and enduring significance of the periodic table. From its early classifications to Mendeleev’s groundbreaking contributions and the modern refinements based on atomic theory, the periodic table remains a testament to human curiosity and the relentless pursuit of knowledge.

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Note: Advertisements and non-content segments were omitted to focus solely on the educational discourse about the periodic table.

Transcript

[Gary Arndt]

The following is an encore presentation of Everything Everywhere Daily. You've seen it in your science classroom and there was probably a copy of it on the inside cover of your chemistry book. Maybe if you're a real nerd, you might even have your own personal copy. Yet its very creation was a revolutionary breakthrough that helped scientists and generations of students understand the very things that make up our world. Learn more about the periodic table of elements and and how it helped explain our natural world on this episode of Everything Everywhere Daily.

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[Gary Arndt]

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[Gary Arndt]

The very first elements were discovered by early humans. The very first ones were all metals. Copper, lead, iron, silver, gold were some of the very first elements that humans recognized. They had no clue what an element was or an atom, but they knew it was a thing. And they knew that one thing like copper was different from another thing like iron. By the time the end of the 18th century rolled around, America was a newly independent country and there were a little over two dozen known elements at the time. In 1789, a French chemist by the name of Antoine Lavoisier made the first systematic attempt at trying to list all of the known elements. He came up with a list of 33 elements and grouped them by known attributes. He primarily divided them into metals and nonmetals. Unfortunately, many of his elements weren't really elements. He included things like light and heat, which weren't even physical things. However, he did get one thing pretty much right. He defined an element as something which could not be broken down any further. Today we call them atoms. As the 19th century began and chemistry became more sophisticated and analytical, there was a rush of new elemental discoveries. Dozens of new elements, usually rare ones, were discovered in the first half of the 19th century. In 1829, German chemist Johann Wolfgang Doberreiner got a little closer. He noticed that many of the elements that displayed similar properties could be grouped into three's and that the atomic weights of the elements were all next to each other. Over the next few decades, as more elements were discovered, chemists noticed that there was a pattern with how elements bonded to each other. For example, carbon could bond to four hydrogen atoms, or it could bond to two oxygen atoms. However, all the attempts to try to organize all of the known elements didn't work. It seemed to make sense in bits and pieces. But when he tried to put it all together, nothing seemed to make sense. In 1860, a conference was held in Germany on the subject of atomic weights. They determined that hydrogen had an atomic weight of one and that every other element would be measured in comparison to hydrogen. In 1862, a French geologist named Alexandre Milbiere de Cinquechois came really close when he noticed that there was a periodicity in the elements. This was a huge step forward in understanding how everything fit together, but it wasn't quite there yet. He actually proposed organizing them in the form of a helix or a screw. The 1860s saw several other attempts at organizing the elements. And each attempt brought something new to the table, which helped describe the elements in relationship to each other. There was one problem, however, that no one had figured out. The big breakthrough in the organization of the elements came from a Russian chemist named Dmitri Mendeleev. In 1869, he published his table, in which he used rows and columns to organize the elements by atomic weight. He would start a new row when attributes started to repeat. The breakthrough element of his chart. And the thing that no one else had really done until this point was that he left empty spaces where there were undiscovered elements. Everyone else just put all the known elements together and that was why everything didn't fit. Mendeleev just let the atomic weight speak for themselves. And if there wasn't a known element that fit, he just assumed that it would be discovered later. By leaving spaces empty. He also guessed at what the general property of the new element in that spot would be. He was also willing to occasionally ignore the order of atomic weights when it made sense and occasionally switched elements around. His first table in 1869 wasn't perfect. He produced another table in 1871 which had more spaces for undiscovered elements. There was also one big unresolved problem. There was a huge gap in atomic weights between the elements cerium and tantalum that he couldn't resolve. At first, no one really gave his table much attention. Then a huge discovery in 1911 really set the periodic table on firm ground. New England physicist Ernest Rutherford discovered the nucleus of the atom. After that, it was suggested that the chart followed the atomic number of the atom, which is the number of protons in the nucleus. It turned out the table was almost already a perfect fit. Based on this new understanding of the periodic table, English physicist Henry Morsley predicted in 1913 that there were still three elements to be discovered between aluminum and gold. His prediction was 100% correct. The last natural element discovered was francium, which was discovered in 1939. That big gap between cerium and tantalum Was finally resolved by Glenn Seaberg in 1942, who identified the rare earth elements, which are usually separated from the rest of the chart at the bottom. They are also known as the lanthanines and actinines. One of the interesting implications of the periodic table is that the last natural element is uranium, with an atomic number of 92. However, there are a bunch of empty spaces beyond the number 92. Unlike the missing elements lower on the chart, these can't be found in nature. So scientists have been working over the decades to make them themselves. The elements closest to uranium can be created via nuclear reactions. However, the farther out you go, the only way to make them is via smashing together other large atoms. As of 2009, researchers have created all of the elements to fill up the table. The last artificial element to be created was element 117, which is called tennessine. The last element on the periodic table is element 118, called Ognisson, and it falls in the same column as the noble gases. All of these artificial elements have extremely short half lives and often don't exist more than a tiny fraction of a second. It isn't known if there are stable elements further out or if there might be stable versions of the atoms that they've already created. So how do you read the periodic table? Starting in the upper left with hydrogen, it goes horizontal by atomic number. Hydrogen is 1. Helium is 2. Lithium is 3. Etc. As I mentioned before, the atomic number is the number of protons in the nucleus, and that's what determines what an element is. Each row is called a period. Each period corresponds to the number of electron shells the element has. The first shell has two electrons in the shell, so there are two elements in the first row. The second and third shells have eight electrons, so there are eight elements in the second and third row. The rare earth elements at the bottom are usually displayed separately, but they do fit on the table. However, if you printed the table with them in their proper place, it would be really, really wide, so it usually isn't presented in that fashion. Each column is known as a group. The group reflects the number of electrons in the upper electron shell. The first column is known as the alkali metals. All of these metals have one electron available and everything in that group is extremely reactive. This includes lithium, sodium and potassium. If you haven't seen it, go look up a video to see what happens to these elements in their pure metallic form when they're placed in water. There are many videos online that show this. They are all explosive, and they get more explosive the further down the group you go. In the last group are the noble or inert gases. They rarely react with anything because their electron shells are full. They include helium, neon, argon, xenon and radon. Metals tend to be on the left side and in the middle. The periodic table is really an amazing thing. It so neatly and cleanly encapsulates how all the elements which make up the world relate to each other. It isn't just a handy educational aid, but it also should be considered an actual thing of beauty.

[Charles Daniel]

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[Gary Arndt]

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