Show Mobile Navigation
Our World |

Top 10 Deadliest Elements in the Periodic Table You Want to Avoid

by Paul Medina
fact checked by Rachel Jones

We’ve all heard about the periodic table. Those colorful squares with cryptic symbols that seemed like hieroglyphics in high school chemistry. But what you might not know is that hidden among the well-known and celebrated elements are some sneaky killers. No, I’m not talking about the stuff you’d find in a spy thriller—it’s the periodic table’s own list of deadly elements. Let’s delve into the world of chemistry’s top ten deadliest elements that often fly under the radar.

Related: 10 Examples Of Chemical Warfare In An Ordinary Garden

10 Polonium: The Rare and Lethal Rock Star of the Periodic Table

Death By Polonium-210 – How Russia Takes Out One of Their Own Spies

Ah, polonium! It’s not your everyday element, that’s for sure. In fact, polonium is so rare and elusive that it’s like the mysterious rock star of the periodic table. Discovered by Marie and Pierre Curie in 1898, this radioactive element gets its name from Poland, as Marie Curie was of Polish descent.

But here’s the kicker: Polonium is incredibly dangerous. It’s so radioactive that even a minuscule amount can wreak havoc on your health. It emits alpha particles, which are like tiny, high-energy wrecking balls for your cells. So, if you ever come across a vial of polonium, I’d recommend giving it a wide berth.

Despite its lethal properties, polonium has found some notoriety in history. You might have heard of the infamous case of Alexander Litvinenko, a former Russian spy who was poisoned with Polonium-210 in London in 2006. That’s right, it’s been a key player in real-life spy thrillers.

So, in the world of elements, polonium is like the enigmatic rock star that you don’t want to party with. It’s rare, dangerous, and linked to some shadowy tales. Best to appreciate it from a safe distance on the periodic table.

9 Caesium: The Alkali Metal with Explosive Reactions and Timekeeping Skills

Alright, let’s talk about caesium or cesium. It’s got atomic number 55, making it a real heavyweight in the alkali metal group. This stuff is no slouch when it comes to reactivity—it can explode on contact with water! Now, that’s a party trick.

Caesium’s claim to fame, though, is its role in atomic clocks. These bad boys are so precise they can measure time to a few billionths of a second. So, next time you’re wondering why you’re always running late, just blame it on caesium—it’s setting the standard for timekeeping.

But don’t go hunting for caesium in your backyard. It’s not exactly a common sight in nature. You’re more likely to find it hiding out in minerals like pollucite. And if you’re into space stuff, caesium comes up in conversations about the geology of celestial bodies. Some asteroids and moons have traces of this element, giving scientists a little cosmic puzzle.

Remember, caesium isn’t exactly something you want to play with for fun. It’s highly reactive, and its radioactive isotopes are a health hazard. So let’s leave the heavy lifting to the scientists and just appreciate caesium for the fascinating element it is!

8 Arsenic: The Notorious Villain of the Periodic Table

The Deadly Trail of Arsenic Through the Ages

Arsenic. The notorious element that’s like the villain of the periodic table. It’s got a dark side. This sneaky element is known for its toxic tendencies, and it doesn’t discriminate—it can harm humans, plants, and even unicorns… if they existed.

Arsenic is naturally found in the earth’s crust, and it’s not uncommon to encounter it in small doses. In fact, it’s sometimes used in semiconductors, wood preservatives, and even in some medicines. But it’s a classic case of “the dose makes the poison.” In high concentrations, arsenic can lead to a not-so-fun lineup of health issues, from skin problems to cancers and worse.

Some might say arsenic has a love-hate relationship with us humans. Historically, it’s been the poison of choice for many a nefarious plot, from murder mysteries to political intrigue. Even Napoleon Bonaparte might’ve tasted it in his final days.

7 Thallium: The Unassuming Toxic Element with a Sinister Nickname


Thallium is an element with a name that sounds more like the title of a Shakespearean tragedy than a chemical element. But don’t be fooled by its fancy moniker—this element is anything but a drama queen.

Thallium sits on the periodic table at atomic number 81, right below mercury. It’s a soft, malleable metal, and if you’ve ever handled it, you’d be forgiven for thinking it’s just another run-of-the-mill silverish element. However, don’t let its unassuming appearance fool you – thallium packs a punch in the toxicity department. In fact, it’s so toxic that it’s been dubbed “the poisoner’s poison.”

But fear not. You’re not likely to stumble upon a vial of thallium in your daily life. It’s not used in any household products, and its main claim to fame is in electronics as a component in some specialized semiconductors. Just remember, when it comes to handling this element, you’re better off leaving it to the professionals.

6 Lead: The Notorious Trouble Maker with a Long History of Harm

Why is Lead Bad For Humans?

Lead—the notorious troublemaker of the periodic table! This heavy metal has a dark side that’s been known for centuries. Let’s get straight to the facts without the frills.

Lead, with the symbol Pb (from the Latin word “plumbum”), is a toxic element that has been causing mayhem for humanity since the Roman Empire. They used it for plumbing, which is where we got the term “plumber,” but they didn’t realize the dangers of lead poisoning back then.

Fast forward to more recent history, and lead is still causing chaos. Remember those old lead-based paints? They were lovely on the walls but horrific for our health, especially for kids who liked to chew on anything in sight. Lead can wreak havoc on the nervous system, causing cognitive and developmental problems. It’s not something you want to play with.

But it’s not all doom and gloom. Lead has some industrial uses, like in batteries and even in radiation shielding. Just don’t chew on your car battery!

5 Francium: The Elusive and Explosive Bad Boy of the Elements

Francium (version 2) – Periodic Table of Videos

Francium is the elusive bad boy of the periodic table! If the elements had a rock band, francium would be the lead guitarist, who’s always late to the gig. Why? Because it’s incredibly rare and incredibly unstable. This radioactive element can’t be found in nature and has a half-life shorter than a TikTok video—just 22 minutes.

Discovered by Marguerite Perey in 1939, francium is like the James Dean of the periodic table, leaving a trail of gamma radiation in its wake. It’s so reactive that it will instantly combust when exposed to air, so don’t expect to find it in your backyard. It’s like the “Here today, gone tomorrow” of the elements.

Don’t underestimate francium’s importance in science. Its reactivity and ability to decay into another element, astatine, make it a valuable tool for studying nuclear reactions. In a way, francium is the daredevil chemist’s dream, even if it’s too unstable to have practical applications.

4 Mercury: The Liquid Marvel with Toxic Secrets

What is Mercury Poisoning? | National Geographic

Mercury is the enigmatic element that’s not just a planet but also a fascinating chemical element! It’s like the James Bond of the periodic table: sleek, shiny, and a bit of a mystery.

First off, it’s the only metal that’s liquid at room temperature. You won’t find a mercury spoon in your kitchen drawer, though. It’s highly toxic, so playing with it is a big no-no.

Mercury’s symbol, Hg, comes from its Latin name, “hydrargyrum,” which means “liquid silver.” Fitting, right? And speaking of silver, it has a stunning silvery sheen that’s mesmerizing.

Mercury has some unusual properties. It forms beautiful, mirror-like droplets, and it’s heavy—13.6 times denser than water. Oh, and don’t even think about freezing it. You’d need to chill it down to a chilly -37.9°F (-38.8°C) for that, and that’s just too much effort.

It’s also been used in thermometers for ages, but we’ve phased that out due to its toxicity. In fact, mercury exposure can lead to serious health issues, so be careful with this liquid marvel.

3 Antimony: The Quirky Element with a Dual Personality


Antimony is the quirky element that’s like the black sheep of the periodic table. It’s got an atomic number of 51 and a name that sounds like it could belong to an eccentric aunt. But don’t let its peculiarities fool you. This stuff has a few tricks up its sleeve.

First, it’s a metalloid, meaning it straddles the line between metals and non-metals. It’s got a bluish-white hue, which is unusual for a metal. And here’s a fun fact: back in the day, people used antimony compounds for various purposes, including cosmetics. They’d put it on their faces, thinking it would give them that coveted pale complexion. Spoiler alert: it wasn’t great for their health.

But here’s where it gets really interesting—antimony has a dual personality. On one hand, it’s used in flame retardants, making it a hero in fire safety. On the other, it’s been known to cause some health issues when ingested in large quantities. So it’s like the firefighter who moonlights as a prankster.

2 Cadmium: A Heavy Metal with Hidden Powers and Dangers

Cadmium – A TOXIC Metal From Old Batteries!

Cadmium is the chemical element with the symbol Cd and atomic number 48. It might not be the life of the periodic table party, but it has its quirks. First, it’s a heavy metal, and not in the “rock ‘n’ roll” sense—this stuff is toxic. You won’t find it as a dietary supplement, but you might encounter it in batteries, pigments, and even some old-school guitar strings.

Now, why should you care about cadmium? Well, it’s got a few tricks up its atomic sleeve. It’s super-duper corrosion-resistant, which makes it a prime candidate for plating other metals to protect them from the elements. You’ll often find cadmium coatings on aerospace parts, ensuring they stay in tip-top shape. And if you’re into nuclear power, cadmium’s your buddy. It can absorb neutrons, making it handy for controlling nuclear reactions.

But here’s the kicker—cadmium can be a real menace if it gets into the environment. It’s notorious for contaminating soil and water, posing a severe risk to ecosystems and human health. So, while cadmium might have some cool chemistry going on, it’s a “handle with care” kind of element.

1 Plutonium: The Radioactive Heavyweight with a Dark History

Plutonium, the Most Dangerous Man Made Element

Alright, let’s talk about plutonium. This element, with atomic number 94, has a bit of a reputation. It’s named after Pluto, the god of the underworld, which should give you a hint about its nature. Plutonium is a radioactive heavy metal, and it’s no lightweight when it comes to potential hazards.

Discovered by Glenn T. Seaborg and his crew in 1940, plutonium has a few tricks. It’s not found in nature, so you won’t stumble upon it during your Sunday hike. No, this bad boy is cooked up in nuclear reactors or synthesized in laboratories.

One of its claims to fame is its use in nuclear weapons, being a key ingredient in the infamous Fat Man bomb dropped on Nagasaki during World War II. Thankfully, it’s also a vital component in nuclear energy production. Plutonium-239, a specific isotope, can undergo fission and generate a ton of energy. It’s like harnessing a tiny sun in a controlled environment.

But don’t be fooled. Plutonium isn’t all doom and gloom. It has its uses in science and industry, too, like powering spacecraft and in certain medical treatments. Just remember, handle with care! It’s not something you want to invite to your dinner party.

fact checked by Rachel Jones