10 Facts About Silicon

iStock
iStock

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.

Silicon is a metalloid: an element with properties not quite like a metal, nor exactly like a non-metal. If you have a cell phone in your pocket or dirt on your shoes, you’re carrying silicon. Learn more about this ever-present element.

1. IT'S JUST ABOUT EVERYWHERE.

It's the seventh most abundant element in the universe and even more prevalent in the Earth's crust, second only to oxygen as the most common element by weight. The layer under the crust—the mantle—is rich in silicon as well. With an atomic number of 14, it sits right below carbon on the periodic table.

2. SILICON ISN'T THE SAME THING AS SILICONE.

silicone breast implant on blue cloth
iStock

The word silicone might make you think of breast implants, but it's actually a general term for a group of synthetic substances made of alternating silicon and oxygen atoms, with carbon and hydrogen molecules bonded on the sides. By mixing up these side groups of molecules and creating links between chains, chemists can create silicones with all sorts of different properties. Yes, you can find silicones in breast implants, but also in car polish, the insulation around electric cables, and even in your hair conditioner, where they help to calm down frizz. We can also thank silicones for Silly Putty, which was invented during World War II, when scientists were trying to create an alternative to rubber—and instead came up with a new national favorite toy.

3. WE USED SILICON FOR THOUSANDS OF YEARS WITHOUT KNOWING ITS ELEMENTAL NATURE.

Silica is the main ingredient of glass, which humans have been making at least since the Egyptians fashioned beads from the material in 2500 BCE. In China, the Qin and Han dynasties used purple and blue pigments made of barium copper silicates for various decorations, including parts of the famous terra-cotta army.

It took many centuries before people realized the substance could be further separated into two different elements—oxygen and silicon. In the late 1700s, French chemist Antoine Lavoisier noticed that certain materials classified as “earth” substances (which were dry and cold) sometimes behaved like metals (hard, dense, and resistant to being stretched, among other qualities). Silica was one of them. Perhaps, Lavoisier mused, some of the earths were really molecules of oxygen and a yet-undiscovered, metal-like element.

At the time, chemists didn’t know how to remove the oxygen atoms, which form strong bonds with the silicon atoms. That changed in the 1820s, when a Swedish chemist named Jons Berzelius finally managed to obtain silicon in his lab by purifying it from a silicon-containing compound. (Which one, and how he did it, isn't clear.) Berzelius's breakthrough came too late for Lavoisier, who had died in 1794, to see his speculations be proven true.

4. SILICA IS THE MOST COMMON FORM OF SILICON.

Also known as silicon dioxide, this molecule is composed of one silicon atom and two oxygen atoms (SiO2). Most of what we call silicon is actually silica, found in both minerals and plants. Many plants create unique microscopic structures called phytoliths using silica they take up from the soil. Scientists aren't sure why: They might offer protection against microscopic harm or provide structural support, or maybe they're just a way for a plant to use up extra silica.

Phytoliths stick around long after a plant decays, which can illuminate the deep history of an area—whether it used to be a forest or grassland, for instance, or how people used the landscape. Dan Cabanes, a phytolith expert and anthropologist at Rutgers University, has used phytoliths to understand how Neanderthals made a home in a cave in northern Spain, creating a sleeping area with grass bedding they used repeatedly. And because phytoliths survive burning, “we can study how they made fire or what type of food they were consuming,” Cabanes tells Mental Floss.

The picture isn’t always perfect, though, because sometimes two different plants make phytoliths of the same shape—and some plants don’t make them at all.

5. IT'S A KEY COMPONENT OF SOME BEAUTIFUL STONES …

close-up of onyx
iStock

Gorgeous gemstones like amethyst, onyx, and agate are all made of silica. In each rock, the silica molecules are arranged in repeating 3D geometries called crystal structures. Different arrangements, as well as small impurities in the rock, give each gemstone its unique appearance.

6. … AND THE DAZZLING BEAUTY OF DIATOMS.

Triceratium polycystinorum diatom
Anatoly Mikhaltsov, Wikimedia Commons // CC BY-SA 4.0

Silica also forms the cell walls of diatoms, a type of algae found all over the world. Diatoms, which come in a mesmerizing variety of shapes, can live in both fresh and saltwater. When they die, their cell walls can accumulate into chalky deposits of "diatomaceous earth," which we use in all sorts of things, from cat litter to toothpaste.

7. SILICON IS VERY USEFUL IN TECH …

Silicon can act as a semiconductor—a material that neither conducts electricity perfectly nor insulates against it, but rather lies somewhere in between. This property is important in many parts of electronics, where you want some control over the flow of electricity. “What's beautiful about semiconductors is that you can tune their conductivity by adding impurities,” Eric Pop, a professor of electrical engineering at Stanford University, tells Mental Floss. Pure silicon is an insulator, but if you ‘dope’ it with tiny amounts of certain other elements, such as phosphorus or arsenic, it becomes better at conducting electricity.

Other materials, including germanium or gallium arsenide, are better semiconductors than silicon, but silicon is the most popular choice among electronics manufacturers (whose concentration south of San Francisco in the 1970s inspired the name "Silicon Valley"). It's cheap, it’s everywhere, and because it likes to oxidize so much, it can conveniently create its own insulating layer when exposed to air.

8. … BUT RESEARCHERS WANT TO FIND BETTER OPTIONS.

Engineers like Pop are looking for materials to replace silicon in our electronics to help keep up with the demand for faster computing. “Silicon is sort of like the Honda Civic of semiconductors,” Pop says. “It gets the job done, but it’s not very fast.” However, Pop thinks that even when pitted against superior materials, silicon won’t completely disappear, thanks to its low cost.

9. SILICON HOLDS UP MANY OF OUR BUILDINGS.

brick building against blue sky
iStock

Many common building materials are based on silicon-containing substances. Clay minerals, which contain silicon, are used to make bricks, as well as Portland cement, which is then used as the binding agent in concrete.

10. AMERICANS LEFT A BIT OF SILICON ON THE MOON.

When Buzz Aldrin and Neil Armstrong became the first humans to walk on the Moon, in 1969, they left a few things on its surface besides their footprints. One was a small silicon disc, inscribed with messages from the leaders of 73 countries, from Afghanistan to Zambia. The disc is housed inside a protective aluminum case and is stashed in a small bag along with a few other items. Silicon was elected official message-bearer because it could endure the huge range of temperatures on the Moon. The disc nearly didn’t make it, though: Aldrin had forgotten all about the bag, tucked into a pocket of his space suit sleeve, and he was already on the ladder to the spacecraft when Armstrong reminded him about it. Aldrin tossed the pouch onto the Moon.

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]

SECTIONS

arrow
LIVE SMARTER