8 Essential Facts About Uranium

Uranium glass vessels.
Uranium glass vessels.
Attila Kisbenedek/AFP/Getty Images

How well do you know the periodic table? Our series The Elements explores the fundamental building blocks of the observable universe—and their relevance to your life—one by one.

Uranium took some time asserting itself. For centuries, heaps of it languished in waste rock piles near European mines. After formal discovery of the element in the late 18th century, it found a useful niche coloring glass and dinner plates. In the first half of the 20th century, scientists began investigating uranium's innate potential as an energy source, and it has earned its place among the substances that define the "Atomic Age," the era in which we still live. Here are some essential facts about U92.

1. IT'S THE HEAVIEST NATURALLY OCCURRING ELEMENT IN THE UNIVERSE.

With a nucleus packed with 92 protons, uranium is the heaviest of the elements. That weight once compelled shipbuilders to use spent uranium as ballast in ship keels. Were it employed that way now, sailing into port could set off defense systems.

Uranium was first found in silver mines in the 1500s in what's now the Czech Republic. It generally appeared where the silver vein ran out, earning it the nickname pechblende, meaning "bad luck rock." In 1789, Martin Klaproth, a German chemist analyzing mineral samples from the mines, heated it and isolated a "strange kind of half-metal"—uranium dioxide. He named it after the recently discovered planet Uranus.

French physicist Henri Becquerel discovered uranium's radioactive properties—and radioactivity itself—in 1896. He left uranyl potassium sulfate, a type of salt, on a photographic plate in a drawer, and found the uranium had fogged the glass like exposure to sunlight would have. It had emitted its own rays.

2. ITS TRANSFORMATIONS PROVED THE ALCHEMISTS RIGHT … A LITTLE.

Uranium decays into other elements, shedding protons to become protactinium, radium, radon, polonium, and on for a total of 14 transitions, all of them radioactive, until it finds a resting point as lead. Before Ernest Rutherford and Frederick Soddy discovered this trait around 1901, the notion of transforming one element into another was thought to be solely the territory of alchemists.

3. IT'S HIGHLY UNSTABLE.

Uranium's size creates instability. As Tom Zoellner writes in Uranium: War, Energy, and the Rock That Shaped the World, "A uranium atom is so overloaded that it has begun to cast off pieces of itself, as a deluded man might tear off his clothes. In a frenzy to achieve a state of rest, it slings off a missile of two protons and two neutrons at a velocity fast enough to whip around the circumference of the earth in roughly two seconds."

4. IF YOU INGEST IT, THANK YOUR KIDNEYS FOR KEEPING YOU ALIVE.

Traces of uranium appear in rock, soil, and water, and can be ingested in root vegetables and seafood. Kidneys take the burden of removing it from the bloodstream, and at high enough levels, that process can damage cells, according to the Argonne National Laboratory. But here's the good news: After short-term, low-level exposures, kidneys can repair themselves.

5. URANIUM MADE FIESTA WARE COLORFUL … AND RADIOACTIVE.

Before we recognized uranium's potential for energy—and bombs—most of its uses revolved around color. Photographers washed platinotype prints in uranium salts to tone otherwise black and white images reddish-brown. Added to glass, uranium gave beads and goblets a canary hue. Perhaps most disconcertingly, uranium makes Fiesta Ware's red-orange glaze—a.k.a. "radioactive red"—as hot as it looks; plates made before 1973 still send Geiger counters into a frenzy.

6. "TICKLING THE DRAGON'S TAIL" WAS KEY TO MAKING THE FIRST ATOMIC BOMBS.

Uranium occurs naturally in three isotopes (forms with different masses): 234, 235, and 238. Only uranium-235—which constitutes a mere 0.72 percent of an average uranium ore sample—can trigger a nuclear chain reaction. In that process, a neutron bombards a uranium nucleus, causing it to split, shedding neutrons that go on to divide more nuclei.

In the 1940s, a team of scientists began experimenting in the then-secret city of Los Alamos, New Mexico, with how to harness that power. They called it "tickling the dragon's tail." The uranium bomb their work built, Little Boy, detonated over the Japanese city of Hiroshima on August 6, 1945. Estimates vary, but the detonation is thought to have killed 70,000 people in the initial blast and at least another 130,000 more from radiation poisoning over the following five years.

The same property that powered bombs is what now makes uranium useful for electricity. "It's very energy dense, so the amount of energy you can get out of one gram of uranium is exponentially more than you can get out of a gram of coal or a gram of oil," Denise Lee, research and development staff member at Oak Ridge National Laboratory, tells Mental Floss. A uranium fuel pellet the size of a fingertip boasts the same energy potential as 17,000 cubic feet of natural gas, 1780 pounds of coal, or 149 gallons of oil, according to the Nuclear Energy Institute, an industry group.

7. THE EARTH CREATED ITS OWN NATURAL NUCLEAR REACTORS BILLIONS OF YEARS AGO.

In the 1970s, ore samples from a mine in what is now Gabon came up short on uranium-235, finding it at 0.717 percent instead of the expected 0.72 percent. In part of the mine, about 200 kilograms were mysteriously absent—enough to have fueled a half-dozen nuclear bombs. At the time, the possibility of nuclear fission reactors spontaneously occurring was just a theory. The conditions for it required a certain deposit size, a higher concentration of uranium-235, and a surrounding environment that encouraged nuclei to continue splitting. Based on uranium-235's half-life, researchers determined that about 2 billion years ago, uranium occurred as about 3 percent of the ore. It was enough to set off nuclear fission reactions in at least 16 places, which flickered on and off for hundreds of thousands of years. As impressive as that sounds, the average output was likely less than 100 kilowatts—enough to run a few dozen toasters, as physicist Alex Meshik explained in Scientific American.

8. AS A POWER SOURCE, IT'S "PRACTICALLY INFINITE."

A 2010 study from MIT found the world had enough uranium reserves to supply power for decades to come. At present, all commercial nuclear power plants use at least some uranium, though plutonium is in the mix as well. One run through the reactors consumes only about 3 percent of the enriched uranium. "If you could reprocess it multiple times, it can be practically infinite," Stephanie Bruffey, a research and development staff member for Oak Ridge National Laboratory, tells Mental Floss. Tons of depleted uranium or its radioactive waste byproducts sit on concrete platforms at nuclear power plants and in vaults at historic weapons facilities around the country; these once temporary storage systems have become a permanent home. 

10 Facts About the Element Lead

iStock.com/aeduard
iStock.com/aeduard

Lead (Pb) is one of the most infamous elements in the periodic table. Though it’s now widely known as the source of lead poisoning, humans have been using the heavy metal for thousands of years. It’s soft, has a relatively low melting point, is easy to shape, and doesn’t corrode much, making it incredibly useful. It’s also relatively abundant and easy to extract. But lead is so much more than just No. 82 on the periodic table. Here are 10 facts about the element lead.

1. The element lead is easy to extract.

One reason people have been using lead for so long is because it’s so easy to extract from galena, or lead sulfide. Thanks to lead’s low melting point of 621.4°F (compare that to the melting point of iron, 2800°F), all you have to do to smelt it is put the rocks in a fire, then extract the lead from the ashes once the fire burns out.

Galena is still one of the major modern sources of lead. Missouri, the biggest producer of lead in the U.S. (and home to the largest lead deposits in the world), designated galena as its official state mineral in 1967. Galena is also the state mineral of Wisconsin, where it has been mined since at least the 17th century. Several towns across the U.S. are named after the mineral as well, most notably Galena, Illinois, one of the centers of the American “Lead Rush” of the 19th century.

2. People have been using lead since prehistory.

The oldest smelted lead object ever found was discovered in a cave in Israel in 2012. Researchers have dated the wand-shaped tool—potentially a spindle whorl—to the late 4000s BCE, tracing its origins to lead ores in the Taurus mountains of what is now Turkey.

3. Lead poisoning can be fatal.

Lead has a fairly similar chemical structure to calcium. Both have two positively charged ions. Because of that, inside the body, the toxic metal can bind to the same proteins as the vital mineral. Over time, lead poisoning occurs as the element crowds out the minerals your body needs to function, including not just calcium, but iron, zinc, and other nutrients.

Lead can travel through the body in the same way that those minerals can, including passing through the brain-blood barrier and into the bones. As a result, exposure to lead—whether through paint, pipes, contaminated soil, or any other means—can be very dangerous, especially for children, for whom lead poisoning can cause learning disabilities, delayed growth, brain damage, coma, and death. Scientists believe there is no safe threshold for lead exposure.

4. Ancient Romans really loved lead.

Lead use reached new heights during the Roman Empire. Ancient Romans used lead to make cookware, water pipes, wine jugs, coins, and so much more. Lead acetate was even used as a sweetener, most often in wine. As a result of ingesting a little lead with every bite of food and sip of water or wine, modern researchers have argued that two-thirds of Roman emperors (as well as plenty of common folk) exhibited symptoms of lead poisoning. A 20th-century examination of the body of Pope Clement II, who died in 1047, showed that lead poisoning led to the religious leader’s sudden demise, too—though there’s still some speculation of whether he was poisoned by an enemy or if he simply drank too much lead-sweetened wine.

5. Lead is a very stable element.

Lead atoms are “doubly magic.” In physics, the numbers 2, 8, 20, 28, 50, 82, and 126 are considered “magic” because those numbers of protons or neutrons completely fill up the atomic nucleus. Lead has 126 neutrons and 82 protons—two magic numbers. As a result, lead isotopes are incredibly stable. Lead-208 is the heaviest stable atom.

6. Lead made car engines quieter—at a high cost.

It’s not surprising that we no longer add lead to gasoline (TIME magazine called it one of the world’s worst inventions back in 2010). But why was it ever there in the first place?

In 1921, a General Motors researcher discovered that adding tetraethyl lead to gasoline reduced “engine knock” in cars, when pockets of air and fuel explode in the wrong place and time in a combustion engine. In addition to producing a loud sound, it also damages the engine. While there were other available chemicals like ethanol and tellurium that could similarly provide the octane boost to reduce knocking, leaded gasoline was easier and cheaper to produce, and unlike tellurium, it didn't reek of garlic.

Unfortunately, it came at a high cost for the refinery workers that produced leaded gasoline (who many of whom were sickened, driven mad, and killed by their exposure to it) and the environment as a whole.

In the 1960s, geochemist Clair Patterson was trying to measure the exact age of the Earth when he discovered a shocking amount of lead contamination in his lab—and everything he tested, from his tap water to dust in the air to his skin and samples of his dandruff. As he continued to experiment, he discovered that lead levels in ocean water began to rise drastically around the same time that lead became a common gasoline additive. Every car on the road was belching lead straight into the atmosphere.

Patterson would later become the driving force in forcing the U.S. government to ban leaded gasoline. (You can read more about him in our feature, “The Most Important Scientist You’ve Never Heard Of.”)

7. Lead was used in paintings …

Historically, lead wasn’t just prized for being an easy-to-shape metal; it was also valued for its color. Though most of us know that lead was historically used in house paint (and still continues to hide in the walls of some homes today), it was also a popular ingredient in fine art for thousands of years.

Produced since antiquity, lead white (also known as Cremnitz white) was a favorite paint pigment of the Old Masters of the 17th and 18th centuries, including artists like Johannes Vermeer and Rembrandt van Rijn.

“For two millennia, white leads—basic lead carbonate and sulfate—were the only white pigments that could deliver moderately durable whiteness and brightness into a drab world of grays and earth colors," pigment experts Juergen H. Braun and John G. Dickinson wrote in the third edition of Applied Polymer Science: 21st Century in 2000. Like a number of other pigments prior to the advent of synthetic paints, its toxicity was general knowledge, but for many painters, the risk was worth it to achieve the color they wanted. You can still buy it today, but it has largely been replaced with the safer titanium white.

Lead white isn't the only lead paint lurking in many famous paintings from history. Dutch artists like Vermeer also favored lead tin yellow, which you can see in his masterpiece The Milkmaid.

8. … and in makeup.

During the 18th century, both men and women used white lead powder to achieve fashionably ghostly complexions, though it was known to be toxic. They powdered their hair with white lead powder, too. The dangerous trend caused eye inflammation, tooth rot, baldness, and eventually, death. To top it off, using lead powder made the skin blacken over time, so wearers needed to apply more and more of the powder to achieve their intended look. Queen Elizabeth I, who lost most of her teeth and much of her hair by the end of her life, reportedly was wearing a full inch of lead makeup on her face when she died. While her cause of death remains unclear, one popular theory holds that she was killed by blood poisoning from her longtime reliance on those lead-filled cosmetics.

Researchers have hypothesized that several other famous historical figures either suffered from or died from lead poisoning, including painters like Vincent van Gogh and Francisco Goya. In several cases, exhumations have proved this: A 2010 analysis of what are thought to be Caravaggio’s bones showed very high levels of lead (enough to drive him crazy, if not outright kill him) likely from his exposure to lead paint throughout his life. Hair and skull fragments believed to belong to Ludwig van Beethoven also show very high lead levels, potentially from the wine he drank.

9. Lead is a superconductor.

Which means that if it is cooled below a certain temperature, it loses all electric resistance. If you were to run a current through lead wire that has a temperature below 7.2K (-446.71°F), it would conduct that current perfectly without losing any energy to heat. A current running through a lead ring could continue flowing forever without an outside energy source.

Like other superconductors, lead is diamagnetic—it is repelled by magnetic fields.

10. On Venus, it snows lead.

Venus is the hottest planet in the solar system, with an average surface temperature of 867°F. That’s far above lead’s 621.4°F melting point. In 1995, scientists discovered what appeared to be metallic “snow” on the mountains of Venus—a planet too hot to have water ice. In 2004, researchers at Washington University in St. Louis discovered that Venusian “snow” was probably a mixture of lead sulfide and bismuth sulfide.

This “snow” forms because Venus’s high temperatures vaporize minerals on the planet’s surface, creating a kind of metallic mist that, when it reaches relatively cooler altitudes, condenses into metallic frost that falls on the planet’s tallest peaks.

How Cold Is It in Canada? Niagara Falls Has Frozen Over

Aaron Vincent Elkaim, Getty Images
Aaron Vincent Elkaim, Getty Images

The cold snap that's gripped the northeast in an icy, subzero chill has made it hard to roll down frozen car windows and navigate roads. Elsewhere, it's having a significantly more spectacular effect: The roaring cascade of water at Niagara Falls at the United States/Canada border has slowed and even come to a stop in some areas, having effectively frozen over.

CNN reports that extreme temperatures have arrested the famous waterfall in spots, creating a kind of winter wonderland that some observers have compared to the handiwork of Elsa in Disney's Frozen. Here's what a similar scene looked like in 2015:

Visitors observe frozen areas of Niagara Falls in 2015
Aaron Vincent Elkaim, Getty Images

And here's a look at footage captured in 2019:

While covered by a sheet of ice, the Falls are not frozen solid: The volume and force of water prevents that. In the 1960s, steel ice booms were added to prevent large blocks from forming farther up the river that could slow the water enough to cause freezing. Instead, it's the surface water and mist that ices over, creating an aesthetically intriguing appearance. If it gets cold enough, ice can form as the water falls, leading to a large deposit on the bottom that can grow to over 40 feet thick.

It's rare for the Falls to come to a complete halt, but before the advent of the ice booms, it was a possibility. On March 30, 1848, gale force winds pushed ice floes from Lake Erie to the mouth of the Niagara River, creating a natural dam and effectively turning off the rushing water. People began walking over the dry riverbed and collected resurfaced weapons from the War of 1812; others thought it was a sign of the end of the world. Niagara Falls has never experienced a near-total interruption since.

[h/t CNN]

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