Place a drop of metal on your palm and watch it run as if alive. This is mercury — the only metal that stays liquid at room temperature. Ancient alchemists called it "quicksilver." Shiny, heavy, and restless, it fascinated people for thousands of years.
But beauty hides danger. Mercury vapor is toxic even in tiny amounts. It damages the brain, kidneys, and nervous system. That is why mercury thermometers are disappearing. Yet mercury still works inside fluorescent lamps, barometers, and chemical plants.
Mercury has been known since the earliest civilizations. It was found in Egyptian tombs and Chinese temples. The main mercury ore is cinnabar (HgS), a bright red mineral. Heating it releases the liquid metal.
Today mercury is tightly regulated. The 2013 Minamata Convention restricts its use worldwide. But a full replacement is not yet possible: mercury is still needed for fluorescent lamps, certain medical instruments, and industrial processes.
Mercury and its vapor are extremely toxic. Even a small spill can poison the air in a room. Chronic inhalation damages the brain and kidneys. Methylmercury in fish caused Minamata disease in Japan — mass poisoning with thousands of victims. Mercury thermometers have been banned in the EU since 2009. Spilled mercury must be collected with a syringe or adhesive tape, never a vacuum cleaner. Ventilation and professional disposal are mandatory.
Mercury is the only metal that is liquid at room temperature. It freezes only at -38.8 °C — colder than the harshest winter on record in most countries.
Mercury is so dense (13.5 g/cm³) that an iron cannonball floats on its surface like a cork floats on water.
Ancient Chinese emperors drank "elixirs of immortality" containing mercury. Emperor Qin Shi Huang likely died from mercury poisoning.
Mercury's Latin name, hydrargyrum, literally means "water silver." That is where the chemical symbol Hg comes from.
A single broken energy-saving bulb contains only 3–5 mg of mercury, but even that tiny amount can push indoor air contamination above safe limits.
The planet Mercury was named after the element (or rather its Roman god) because it races across the sky just as a drop of quicksilver races across a table.
| Isotope | Mass (u) | Abundance | Half-life | Decay |
|---|---|---|---|---|
196Hg | 195.965833 | 0.15% | stable | — |
198Hg | 197.966769 | 9.97% | stable | — |
199Hg | 198.968280 | 16.87% | stable | — |
200Hg | 199.968326 | 23.10% | stable | — |
201Hg | 200.970302 | 13.18% | stable | — |
202Hg | 201.970643 | 29.86% | stable | — |
204Hg | 203.973494 | 6.87% | stable | — |
Known since antiquity