8. Oxygen: Take What You Can Get

 

Element 8 brings us two stories of a population that gets a little too swept up in the latest craze, happening to commit mass murder in the process.

Featured above: A painting of Antoine Lavoisier and his wife, Marie Anne.

Episode Script

The most abundant element in the universe is the first element, hydrogen. The second-most abundant element in the universe is the second element, helium. The third-most abundant element in the universe is element eight, oxygen. This irritating fact tends to undermine any simple explanations. In fact, for a long time, it seemed like there was no explanation — the universe just happens to be a capricious place, sometimes.

But Maria Goeppert-Mayer thought she might have an explanation.

Goeppert-Mayer was a seventh-generation scientist whose career spanned the mid-twentieth century. In the 1940s, she saw a similarity between atoms with certain numbers of protons and neutrons, and the way electrons prefer to have full valence shells. She was on the right track. There’s a lot of complex math going on behind the scenes, but there are certain “magic numbers” of protons and neutrons that lend extra stability to a nucleus. These numbers are 2, 8, 20, 28, 50, 82, and 126. Nitrogen-15 is an isotope of nitrogen that’s quite stable, because it has eight neutrons in addition to its seven protons.  Oxygen has eight protons and eight neutrons, so it’s said to be “doubly magic”  — in other words, extra stable. This extreme stability is why there’s so much oxygen in the universe: It sticks around for a really long time.

Goeppert-Mayer had broken new ground in physics, but — much like Clara Immerwahr — because she was a woman, she struggled to be taken seriously. Even when she earned a teaching position at the University of Chicago, she wasn’t given a paycheck for her work. So it’s not surprising that when she introduced her nuclear shell theory, it wasn’t taken very seriously.

When a group of German scientists made the same discovery, they easily could have left Goeppert-Mayer in the dust and taken all the credit. After all, they might have reached the same conclusion, but they did so completely independently. The Germans decided not to do this, however, instead offering to share the credit with Goeppert-Mayer. Thanks to their good will — and her own sharp mind, of course — Maria Goeppert-Mayer became the second of only two women to ever win a Nobel Prize in physics. The other was Marie Curie.

That is some elite company to be keeping, but even after winning the highest honor her field had to offer, the compliments she received could still be backhanded. Her local San Diego newspaper reported the story with the headline, “S. D. Mother Wins Nobel Prize.”1

That’s a pretty patronizing way to honor a brilliant scientist’s achievements, but surely insult is preferable to injury. Unfortunately, that’s what was in store for someone else who famously studied oxygen.

You’re listening to The Episodic Table Of Elements, and I’m T. R. Appleton. Each week, we take a look at the fascinating true stories behind one element on the periodic table.

Today, we aspire to learn about oxygen.

The last few elements we’ve examined have been relatively tame. Boron isn’t terribly reactive. Carbon will hook up with any old atom, but isn’t very loud about it. The most common form of nitrogen is practically an inert gas. Today, with the first element of the chalcogen group, things get spicy again.

Oxygen is not the most reactive element on the table, but it’s probably the most common reactant on the planet. It is, of course, an integral part of all the water on earth, and it also comprises a quarter of the Earth’s atmosphere, so pretty much everything on the planet mixes with oxygen sooner or later.

But it wasn’t always so common.

Our planet has been around for about four and a half billion years, but it hasn’t always been the pleasant, warm garden of paradise it is today. In its earliest days the Earth was a giant ball of hot lava. When things finally cooled down, it was little more than a barren, wet rock. The seas looked like blood from the incredible amounts of rust in the water. There was an atmosphere, but it didn’t contain any oxygen. By two and a half billion years ago, the air was mostly composed of carbon dioxide, with a smattering of ammonia and methane floating about.2

Despite this hostile environment, life still managed to gain a foothold. The predominant form was anaerobic bacteria — that is, bacteria that does not use oxygen in any way. Life had gone on like this for hundreds of millions of years. But near the surface of the rust-red seas, one microbe was taking a different approach.

The cyanobacteria exploited the energy of the sun. They were the first life forms to develop photosynthesis. They harvested light for energy and gave off oxygen as waste — kind of like plants do today. This wasn’t a big deal… at first. But the cyanobacteria were sixteen times more efficient at metabolizing energy than their anaerobic counterparts. It wasn’t long before the seas and the air were saturated with oxygen.

That was a bit of a problem for the anaerobes. It’s not just that oxygen was useless to them — oxygen was actually poisonous to them. They started to die off. Scientists call this The Great Oxygenation Event, or sometimes, a bit more colorfully, The Oxygen Catastrophe. But it wasn’t just the newly toxic air that was hazardous for their health.3

Some of the airborne oxygen combined with the already-present methane to form carbon dioxide. This caused Earth’s climate to change in a way that might surprise you: Methane is a much more effective greenhouse gas than CO2, insulating the Earth to a greater degree. So converting most of it to carbon dioxide actually cooled the earth, to the point that this era is called “Snowball Earth.”

Between the poison air and the global freeze, the anaerobes didn’t have a chance. The cyanobacteria had kicked off the world’s first mass extinction. What few were able to survive retreated to the darkest corners of the earth, locked far away in caves or the deepest trenches of the ocean. The rest of the Earth belonged to the oxygen-breathers.4

Oxygen was toxic to anaerobic bacteria and beneficial for respiring organisms for the same reason: it’s all around us, and it’s pretty reactive. This makes it a convenient vehicle to shuttle electrons from one part of the body to another.

Oxygen’s valence shell is missing two electrons, and it’ll bully other atoms around to get them. This is such a common occurrence that whenever an atom loses electrons — like, if oxygen is taking them — it’s called “oxidation.” The opposite, gaining electrons, is called “reduction.” It’s a little counter-intuitive.

There are several mnemonics to help keep this straight. When I took high school chemistry, Brother Xavier Pankovits taught us “LEO the lion says GER,” for “Losing Electrons Oxidation,” “Gaining Electrons Reduction.” A more intuitive acronym, in my opinion, is “OIL RIG”: Oxidation Is Losing, Reduction Is Gaining. But there are also stranger mnemonics, including “RED CAT gains what AN OX loses,” and the stupefying, “LEORA says GEROA.” At that point it seems you’d need a mnemonic to remember your mnemonic, which really defeats the whole purpose. But I suppose this is what passes for wit in chemistry circles.

Oxidation and reduction are complementary processes, flip sides of the same coin. One atom can’t undergo oxidation without another also undergoing reduction. So sometimes, these are simply called “redox reactions.”

Redox reactions can happen quickly or slowly. When iron is left out in the elements for a long time, it forms ferrous oxide — commonly known as rust. When a material like wood or cloth oxidizes rapidly, it forms fire.

You actually can’t start a fire without some kind of oxidizer. It doesn’t need to be oxygen, but usually is. This oxidizer rips electrons away from the source of fuel in the presence of heat.

Sometimes this is called the “fire triangle,” illustrating that a fire cannot ignite if fuel, heat, and oxidizer are not all present. Considering fire is among humanity’s earliest discoveries, it’s a little surprising that we’ve only come to a thorough understanding of the phenomenon in the past few centuries.

Before the discovery of oxygen, no one could really figure out what fire is. The prevailing theory involved a theoretical substance called “phlogiston” that existed in certain materials, and when liberated, it released flames and left ash behind. This was only a little more sophisticated than the classical elemental theory, and the confusion around the idea probably caused some delay in the discovery of oxygen.

As with practically everything in science, there’s a considerable lineup of scientists who independently discovered oxygen, going as far back as the 16th century. Michael Sedziwoj, Cornelius Drebbel, Carl Wilhelm Scheele, and Joseph Priestley all play important roles in the history of the element, and each could fill an entire episode on their own, but today we’ll be talking about Antoine Lavoisier.

Lavoisier was a man of many talents, but he’s particularly important to the history of chemistry. He was born in Paris, France, in 1743, to a very wealthy family. He pleased his father by marrying into another very wealthy family, and going to law school. This social climbing led to some lucrative government jobs — particularly regarding the taxation of tobacco and salt.5

His job was one that most men abused, skimming a lot of money off the top and not getting punished for it. Conversely, Lavoisier didn’t engage in this kind of activity. He actually enacted a lot of standards and reforms that ensured citizens and customers weren’t overpaying for their goods. This was wonderful for the people, but it did make him fairly unpopular with the merchants.6

Just because Lavoisier had a conscience didn’t mean he was suffering, exactly. He had enough money to conduct elaborate science experiments and commission equipment that cost exorbitant sums of money. If you didn’t know the context for some of these experiments, they might sound ludicrously extravagant — like the time he set a diamond on fire.

Lavoisier conducted landmark work with several elements: Hydrogen, as we heard in episode 1, as well as phosphorus, sulfur, carbon, and oxygen. It was an experiment with the latter two that led to the combustible bauble.

He and some fellow scientists pooled their money and bought a diamond, contained it in a sealed flask of pure oxygen, and set it beneath an enormous magnifying lens. The lens focused the energy of the sun on the gemstone. With heat, fuel, and oxygen thus brought together, the diamond disappeared in a puff of smoke, combining with the oxygen to form carbon dioxide. This wasn’t just flashy showmanship. It showed  that diamonds were pure carbon, proved the existence of allotropes, and was part of Lavoisier’s years-long study of combustion. Notably, the weight of the container hadn’t changed at all. This knowledge, along with findings from later experiments, brought Lavoisier to this conclusion:

Nothing is created, either in the operations of art or in those of nature, and it may be considered as a general principle that in every operation there exists an equal quantity of matter before and after the operation; that the quality and quantity of the constituents is the same, and that what happens is only changes, modifications. It is on this principle that is founded all the art of performing chemical experiments; in all such must be assumed a true equality or equation between constituents of the substances examined, and those resulting from their analysis.”

Or, to simplify a bit, “Matter can neither be created nor destroyed.” You might know this as the Law of Conservation of Matter, but French chemistry students learn it as Lavoisier’s Law.7 8

He racked up many more scientific accomplishments over the course of his career, like debunking the phlogiston theory, naming oxygen and proving its role in combustion, helping devise the metric system, and inventing a pleasant new way to illuminate the streets of Paris, famously known as the City of Lights. He helped turn the mysticism of alchemy into the science of chemistry. And unlike most of his 18th-century contemporaries, the majority of his work has stood the test of time. He was assisted in these endeavors by his wife, Marie Anne Lavoisier, who was enthusiastic about science and fluent in English. She translated correspondence with other luminaries of the era, and was a capable lab assistant, too.9

As a member of the French Academy of Sciences, Lavoisier suffered no fools — and he knew how to spot ’em. When an upstart physician named Franz Friedrich Anton Mesmer started promoting bogus theories of “animal magnetism” and hypnotism that could cure diseases, Antoine Lavoisier teamed up with Joseph-Ignace Guillotin and Benjamin Franklin to debunk the hokum — and in the process, they just so happened to invent the controlled clinical trial, a method of testing that’s still used in the sciences today.10

Mesmer’s lasting legacy wound up being his name, for someone entering a hypnotic daze is said to be mesmerized.

This shattered the hopes of Jean-Paul Marat, a poor young man and one of Mesmer’s disciples. It had been his application to the Academy of Sciences that led to the Lavoisier/Guillotin/Franklin commission, and needless to say, he was not accepted as a member. From a scientific standpoint, this was clearly the right decision to make. Unfortunately for Lavoisier, Marat was a man who held the kind of grudges that make history.11

His scientific career was effectively over, so Marat turned to the political arena, where, amidst the fomenting unrest of revolutionary France, he found greater success. It’s actually difficult to say if the tumultuous time was beneficial for such a bitter man’s career, or if Marat was so bitter that he actively made France a more tumultuous place.12 Suffice it to say, Marat’s journalism makes modern-day public discourse look almost civil.

He decried Lavoisier in the press, calling his science fraudulent and accusing him of exactly the kind of corruption that he didn’t commit. Perhaps it was easy to believe these lies about a wealthy tax collector who had married into a wealthy family, a man who publicly vaporized diamonds. Marat campaigned for the dissolution of the entire French Academy of Sciences. But worse, Lavoisier’s name appeared next to supposed traitors suspected of conspiring with foreign powers to quash the French Revolution. And Marat wasn’t just trying to shame those people. He was calling for their public execution by guillotine.13

You are probably familiar with the guillotine. It’s a simple device, consisting of a heavy, sharp, angled blade that reliably slides swiftly down its frame, decapitating its restrained victim. It was not invented by Joseph-Ignace Guillotin. The basic idea for the guillotine has been around since the Roman Empire, and the specific prototype used in France was first built by a surgeon named Antoine Louis. But Guillotin, the same one who worked with Lavoisier and Franklin to keep Marat out of the Academy, was a member of the design committee — if that’s what you’d call such a group. He spoke publicly about how this was a relatively humane method of execution.

The next day, a song was released mocking Guillotin’s earnest support for the device. A 19th-century English translation goes,

Politician,
And physician,
Bethought himself, ’tis plain,
That hanging’s not humane
Nor patriotic;
And straightaway showed
A clever mode
To kill – without a pang – men;
Which, void of rope or stakes,
Suppression makes
Of hangmen. …

And then offhand,
His genius planned
That machine that ‘simply’ kills—that’s all—
Which after him we call
“Guillotine”

It was a hit, and it’s really because of this silly song that Joseph-Ignace Guillotin’s name is synonymous with the execution device.

Despite the gaffe, Guillotin wasn’t actually wrong about how humane the device was  — again, relatively speaking. In pre-revolutionary France, commoners were executed either by hanging, or by a torture device called “The Breaking Wheel.” Nobles were beheaded using swords or axes. It may not sound like a big difference between an axe and a guillotine, but it is for the person whose head is on the chopping block. Axes and swords were historically not particularly sharp blades, and they depend on the executioner’s ability to aim, which was often questionable. Without getting too gruesome, many beheadings required more than one blow to get the job done.

So, yes, compared to all that, the guillotine looked downright friendly. Even so, Guillotin himself actually hated the idea. He was opposed to capital punishment in all forms, and merely hoped that the guillotine would be an egalitarian and short-lived step on the road to the abolition of execution. When it quickly became obvious that this was not going to happen, Guillotin and his family were embarrassed by their own name. After Guillotin died, his children petitioned the French government to officially change the name of the guillotine to anything else — and when they flatly refused, the family changed their name to Mercier.14

As a quick aside, it’s sometimes claimed that Guillotin was a victim of the guillotine, but this is false. Of all the characters in this story, he’s actually the only one to survive into the 19th century, and he died from a decidedly unglamorous case of staph infection. So just to set the record straight, Joseph-Ignace Guillotin was not killed by the machine he did not invent.

Anyway, the French government had this shiny new way to kill people, and most folks had one of two reactions: Either, “This thing kills people so quickly, they won’t suffer,” or, “This thing kills people so quickly, we can kill a lot more people.” Marat fell into the second camp.

At one point, he thought France would be much better off following the deaths of 200 people. But it didn’t take long for that number to reach two hundred thousand. His extreme views sold pamphlets, but after long enough, his views no longer seemed so extreme. When heads began to roll, he was deservedly quick to take the credit.

Shockingly, not everyone was on board with mass executions. Charlotte Corday was a young woman and moderate republican who wanted to end the blood-fueled craze. She paid a visit to Marat in Paris, and while he soaked in a medicinal bath, Corday stabbed him once, fatally, through the carotid artery. She hoped that with this assassination, a hundred thousand more could be prevented.

Corday did not flee. Her trial was quick; she was proud and unrepentant. Four days after Marat’s death, Corday was executed by guillotine. She expected this to happen, and accepted her fate. What she hadn’t realized was that she had just created a martyr. If anything, Marat’s murder was the perfect culmination of his life as a propagandist. Artists painted him as a Christ-like figure, and the bathtub in which he died was put on display at his funeral, as though it were his own crucifix. And his still-living friends felt even more righteous and emboldened.15

None of this was good news for Antoine Lavoisier. It wasn’t long before he was imprisoned and given a show trial even quicker than Charlotte Corday’s. In what may be an apocryphal anecdote, several of Lavoisier’s friends testified on his behalf, rightly claiming that executing Lavoisier would deprive France of a legendary scientist. The president of the tribunal is said to have replied, “The Revolution has no need for scientists!” Antoine Lavoisier was only 50 years old on May 8, 1794, when his life was tragically cut short.16


If you’e got a particularly clever head on your shoulders, you might have already added oxygen to your collection. Back in episode one, we split water to collect hydrogen bubbles forming on the underwater cathode of our electrical circuit. Meanwhile, oxygen from those cracked water molecules was collecting on the negative anode. If you surmised this at the time and kept some of those bubbles in another container, congratulations! You’ve already finished this week’s homework.

But if you didn’t, and you don’t feel like performing an experiment you already conducted months ago, don’t fret. There are some alternative ways to collect oxygen. Obviously, like nitrogen, you’re breathing it all the time. Unlike nitrogen, your life depends on it. If you happen to breathe an air mixture that has no nitrogen in it, like some deep-sea divers do, you’ll be just fine. If you still hear my voice, you’re probably doing a great job of finding air with plenty of oxygen in it.

The other gases in Earth’s atmosphere exist only in trace amounts, so if you’ve been counting on your lungs to do the collecting for you these past two episodes, this is the last time you can get away with that cop-out.

The discerning collector will need to look back to a bygone era of pogs, slap bracelets, and Trapper Keepers, because the last time pure oxygen was a fad was sometime in the 1990s. That was when oxygen bars started popping up all over America, promising to fill their visitors with vim and vigor by supplying them with breathable air that was 100% oxygen, as opposed to the piddly 24% present in regular air. File this one firmly in the “snake oil” category of elemental medicine, because there’s no proof that breathing pure oxygen does much of anything for you — unless, of course, you’re dealing with lung disease, or climbing Mount Everest.

At any rate, pure oxygen shouldn’t be too difficult to get a hold of. But those are all samples of diatomic oxygen, O2. There is another important allotrope of oxygen present on Earth: a trio of oxygen atoms bonded together in a molecule called “ozone.” It gets this name from the Greek “ozein,” meaning “to smell,” because O3 has a distinct and noticeable odor. You don’t want to breathe in too much of the stuff, though, because it has a tendency to burn the body’s sensitive mucous membranes.

For our sakes, then, it’s a good thing that most of the world’s ozone tends to accumulate high in the Earth’s stratosphere, dozens of kilometers overhead, where it’s formed when high-energy ultraviolet light from the sun reacts with molecules of O2. There, ozone performs an important role in preventing much of that ultraviolet light from striking the Earth’s surface, where it could burn our sensitive skin and damage our DNA. In fact, speaking of the 90s, it was around that time that scientists noticed a rather large and worrisome hole in the Earth’s ozone layer — partly due to our use of chemicals called “chlorofluorocarbons.” We’ll learn more about those next time, but for now, if you’ve been pulling ozone from the stratosphere to add to your element collection, we would all really appreciate it if you wouldn’t mind putting it back.

Thanks for listening to the Episodic Table of Elements. Music is by Kai Engel. We’re going to stick with the every-other-week schedule for now, so we’ll be back on Monday, March 15, when we’ll go with the fluorine.

This is T. R. Appleton, reminding you to protect ya neck.

Sources

  1. APS News, December: Women And The Nobel Prize In Physics. Michael Lucibella, December 2013.
  2. Arizona State University, The Oxygenation Catastrophe. Ryan Casey, February 5, 2015.
  3. BBC Earth, The Event That Transformed Earth. Michael Marshall, July 2, 2015.
  4. Slate, Poisoned Planet. Phil Plait, July 28, 2014.
  5. Encyclopedia Britannica, Antoine-Laurent Lavoisier. Arthur L. Donovan, last updated October 18, 2017.
  6. Lavoisier, Antoine Laurent. David Darling.
  7. World Of Chemicals, Antoine Lavoisier – Father Of Modern Chemistry.
  8. Chem Team, Lavoisier And The Law Of Conservation Of Mass.
  9. Famous Scientists, Antoine Lavoisier.
  10. Urologic Oncology, Franklin, Lavoisier, And Mesmer: Origin Of The Controlled Clinical Trial. Harry W. Herr, M.D. September – October, 2005.
  11. Unintentional Irony, Lavoisier. November 9, 2007.
  12. The answer, of course, is probably “both.”
  13. Encyclopedia Britannica, Jean-Paul Marat. Jean Vidalenc, last updated February 24, 2017.
  14. The Atlantic, The Death-Penalty Abolitionist Who Invented The Guillotine. Naomi Russo, March 25, 2016.
  15. Mental Floss, 15 Things You Should Know About The Death Of Marat. Kristy Puchko, June 12, 2015.
  16. io9, The Scientific Feud That Ended In An Execution. Esther Inglis-Arkell, June 28, 2013.

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