Worst Elements on the Periodic Table

Worst Elements Known To Man

You might think the worst chemical elements might offer some sort of warning, like smoke or a radioactive glow. Nope! Most are invisible or innocuous-looking.
You might think the worst chemical elements might offer some sort of warning, like smoke or a radioactive glow. Nope! Most are invisible or innocuous-looking. WIN-Initiative, Getty Images

There are 118 known chemical elements. Some of them you need in order to survive, others are downright nasty. What makes an element "bad"? There are three broad categories of nastiness. The obviously dangerous elements are those which are highly radioactive. While radioisotopes can be made from any element, you'd do well to steer clear of any element from atomic number 84 (polonium) all the way to element 118 (which is too new to have a name yet). Then there are elements which are dangerous because of their inherent toxicity and those that present a risk because of extreme reactivity.

Ready to meet the baddies? Take a look at the worst of the worst, how to recognize these elements, and why you need to try your hardest to steer clear of them.

Polonium Is One Nasty Element

Polonium isn't much worse than any other radioactive element, until it gets inside your body!
Polonium isn't much worse than any other radioactive element, until it gets inside your body!. Steve Taylor/Getty Images

Polonium is rare, radioactive metalloid that occurs naturally. Of all the elements on the list, it's the one you're least likely to meet in person, unless you work at a nuclear facility or are a target for assassination. The element is used as an atomic heat source, in anti-static brushes for photographic film and industrial manufacturing, and as a nasty poison. Should you happen to see polonium, you might notice something is a bit "off" about it because it excites molecules in air to produce a blue glow. The alpha particles emitted by polonium-210 don't have enough energy to penetrate skin, but the element emits a lot of them. 1 gram of polonium emits as many alpha particles as 5 kilograms of radium. The element is 250 thousand times more toxic than cyanide. So, one gram of Po-210, if ingested or injected, could kill 10 million people. Former spy Alexander Litvinenko was poisoned with a trace of polonium in his tea. It took 23 days for him to die. Polonium is not an element you want to mess around with.

Fun Fact: While most people are aware Marie and Pierre Curie discovered radium you might be surprised to know the first element they discovered was polonium.

Mercury Is Deadly and Omnipresent

Mercury metal can be absorbed through your skin, but organic mercury is a much more common threat.
Mercury metal can be absorbed through your skin, but organic mercury is a much more common threat. CORDELIA MOLLOY, Getty Images

There's a good reason you don't find mercury in thermometers much anymore. Mercury is located right next to gold on the periodic table, but while you can eat and wear one, you'd do best to avoid the other. The toxic metal is dense enough that it can be absorbed into your body directly through your unbroken skin. The liquid element has a high vapor pressure, so even if you don't touch it, you absorb it through inhalation. Your biggest risk from this element isn't from the pure metal, which you can recognize on sight, but from organic mercury that works its way up the food chain. Seafood is the best-known source of mercury exposure, but it's also released into the air from industries, such as paper mills.

What happens when you meet up with mercury? The element damages multiple organ systems, but the neurological effects are the worst. It affects memory, muscle strength, and coordination. Any exposure is too much, plus a large dose can kill you.

Fun Fact: Mercury is the only metallic element that is a liquid at room temperature.

Arsenic Is a Classic Poison

Arsenic may be the element best-known as a poison.
Arsenic may be the element best-known as a poison. Buyenlarge, Getty Images

People have been poisoning themselves and each other with arsenic since the Middle Ages. In Victorian times, it was a poisoner's obvious choice, but people also exposed themselves to it from paints and wallpaper. In the modern era, it's not useful for homicide (unless you don't mind getting caught) because it's easy to detect. The element is still used in wood preservatives and certain pesticides, but the greatest risk is from groundwater contamination, most often resulting when wells are drilled into arsenic-rich aquifers. It's estimated 25 million Americans and as many as 500 million people worldwide drink arsenic-contaminated water. Arsenic may well be the worst element, in terms of public risk.

Arsenic disrupts ATP production (that molecule your cells need for energy) and causes cancer. Low doses, which may have a cumulative effect, cause nausea, bleeding, vomiting, and diarrhea. A large dose causes death, but it's a slow and painful demise that usually takes hours.

Fun Fact: While deadly, arsenic was used to treat syphilis because it was vastly superior to the old treatment, which involved mercury. In the modern era, arsenic compounds show promise in treating leukemia.

Francium Is Dangerously Reactive

Francium and other alkali metals react vigorously with water. The pure element would like explode on contact with skin.
Francium and other alkali metals react vigorously with water. The pure element would like explode on contact with skin. Science Picture Co, Getty Images

All of the elements in the alkali metal group are extremely reactive. You'll get a fire if you put pure sodium or potassium metal in water. The reactivity increases as you move down the periodic table, so cesium reacts explosively. Not much francium has been produced, but if you had enough to hold the element in the palm of your hand, you'd want to wear gloves. The reaction between the metal and the water in your skin would make you a legend in the emergency room. Oh, and by the way, it's radioactive.

Fun Fact: Only about 1 ounce (20-30 grams) of francium can be found in the entire Earth's crust. The amount of the element that has been synthesized by mankind isn't even enough to weigh.

Lead Is a Poison You Live With

Lead is used in or contaminates so many products, it's impossible to completely avoid exposure.
Lead is used in or contaminates so many products, it's impossible to completely avoid exposure. Alchemist-hp

Lead is a metal that preferentially replaces other metals in your body, like the iron, calcium, and zinc you need to function. In high doses, exposure can kill you, but if you're alive and kicking, you're living with some of it in your body. There's no real "safe" level of exposure to the element, which is found in weights, solder, jewelry, plumbing, paint, and as a contaminant in many other products. The element causes nervous system damage in babies and children, resulting in developmental delays, organ damage, and reduced intelligence. Lead doesn't do adults any favors either, affecting blood pressure, cognitive ability, and fertility.

Fun Fact: Really, this fact isn't so fun. Lead is one of the few chemicals known with no safe threshold for exposure. Even minute quantities cause harm. There is no known physiological role played by this element. One interesting fact is that the element is toxic to plants, not just animals.

Plutonium Is a Radioactive Heavy Metal

Plutonium may appear as a silver-colored metal, but it may oxidize in air (burn really) so that it appears like a glowing red ember.
Plutonium may appear as a silver-colored metal, but it may oxidize in air (burn really) so that it appears like a glowing red ember. Los Alamos National Laboratory

Lead and mercury are two toxic heavy metals, but they aren't going to kill you from across the room (okay, I lied... mercury is so volatile it actually might). Plutonium is like the radioactive big brother to the other heavy metals. It's poisonous on its own, plus it floods its surrounds with alpha, beta, and gamma radiation. It's estimated 500 grams of plutonium, if inhaled or ingested, could kill 2 million people. That's not nearly as toxic as polonium, but plutonium is more abundant, thanks to its use in nuclear reactors and weapons. Like all of its neighbors on the periodic table, if it doesn't kill you outright, you may experience radiation sickness or cancer.

Fun Fact: Like water, plutonium is one of the few substances that increases in density when melted from a solid into a liquid.

Helpful Tip: Don't touch metals that are glowing red. The color may mean they are hot enough to be incandescent (ouch) or it may be an indication you're dealing with plutonium (ouch plus radiation). Plutonium is pyrophoric, which basically means it has a tendency to smolder in air.