Which metal is liquid at room temperature?

The Only Metal That Flows at Room Temperature

Mercury is one of the most fascinating substances on the periodic table. While virtually every other metal you can think of — iron, copper, gold, aluminum — is a solid at room temperature, mercury sits in a bowl and sloshes around like water. It has a melting point of just −38.83°C (−37.89°F), meaning it has already been liquid for a very long time before it ever reaches your kitchen counter.

Why Is Mercury a Liquid?

The secret lies in mercury's atomic structure. Mercury has a completely filled set of electron orbitals, which makes its atoms relatively reluctant to bond strongly with each other. The metallic bonds holding mercury atoms together are unusually weak compared to other metals. Add in effects from Einstein's special relativity — yes, really — and things get even stranger. Mercury's electrons move so fast that relativistic effects cause its outer orbitals to contract and become less available for bonding. The result? A metal that barely holds itself together, and flows freely at everyday temperatures.

A Metal With a Very Long History

Humans have known about mercury for thousands of years. It was found in Egyptian tombs dating back to around 1500 BCE. Ancient civilizations were captivated by its bizarre, mirror-like appearance and fluid movement, and it earned the nickname quicksilver — a nod to both its speed and its silvery sheen. The chemical symbol for mercury, Hg, comes from the Latin hydrargyrum, meaning "water silver."

For centuries, mercury played a central role in medicine, mining, and manufacturing. Gold and silver miners used it to extract precious metals from ore through a process called amalgamation, since mercury readily dissolves both metals. Alchemists were obsessed with it. Physicians prescribed it as a treatment for syphilis and other diseases — a practice that, unsurprisingly, caused its own wave of poisonings.

Mercury in the Modern World

Even today, mercury has practical uses. It was the go-to liquid in thermometers and barometers for centuries, thanks to its consistent expansion rate and high density. Fluorescent light bulbs contain small amounts of mercury vapor. It's used in certain types of electrical switches and in the production of chlorine gas and caustic soda.

That said, mercury is seriously toxic. It attacks the nervous system, kidneys, and brain. Exposure to mercury vapor is particularly dangerous because it's invisible and odorless. The phrase "mad as a hatter" traces back to 19th-century hat makers who used mercury nitrate to cure felt and suffered neurological damage as a result.

One of a Kind

Under normal conditions, mercury stands alone as the only metal that is liquid at room temperature. Gallium comes close — it melts at just 29.76°C (85.57°F) and will liquefy in the warmth of your hand — but mercury doesn't need any help at all. It arrives liquid and stays that way, a genuinely unique element that has captured human curiosity for millennia.