Mercury (Hg)
“The only metal that runs like water and shines like silver — and whose invisible vapour taught the world the meaning of “poisoning”.”
How its electrons are arranged
Computed from the aufbau principle, with known real-world exceptions applied automatically.
The notes
Characteristics
- Liquid at room temperature because its 5d¹⁰ 6s² shells are filled and grip their electrons tightly — metallic bonding is so weak that the metal flows apart above −39 °C.
- It swallows many other metals to form amalgams: silver–tin amalgam filled teeth for a century, and artisanal gold miners still bind gold into a mercury paste — a banned but stubborn practice.
- The vapour is a silent poison — colourless, odourless, accumulating in nerves and kidneys; “mad as a hatter” remembers hat-makers shaking from mercury nitrate, and Minamata’s fish-borne epidemic showed methylmercury climbing the food chain.
- Chemically aloof yet even-tempered: it ignores dilute acids that eat iron, but expands smoothly and uniformly with temperature — the very property that made it the world’s thermometer fluid.
A heavy, silvery liquid — the only metal that is liquid at room temperature, freezing only at −39 °C. Its surface tension is so high that spilled mercury breaks into skittering beads, and a one-litre bottle of it would drag the scale to about 13.5 kilograms.
Where you meet it
✦ Uses
- Thermometers, blood-pressure gauges and Torricelli-style barometers — the silver thread that measured fevers and weather alike for three centuries, now surrendering to digital sensors under the Minamata Convention, to which Bangladesh is a party.
- Fluorescent tubes and CFL bulbs: the electric discharge through mercury vapour gives ultraviolet, and the phosphor coating on the glass turns that UV into white light.
- Dental amalgam — mercury triturated with a silver–tin alloy — set into fillings that served hundreds of millions of teeth through the twentieth century.
- The classical calomel reference electrode of potentiometry, and the historic gold-miner’s amalgam trap for catching alluvial gold before cyanide leaching took over.
◍ Everyday examples
- The old glass thermometer rolling in the family medicine box, its silver thread of mercury, is now handed in as hazardous waste rather than binned.
- Each classroom or office fluorescent tube carries a few milligrams of mercury vapour — the reason broken tubes go to special recycling, never to the open bin.
- Traditional red sindoor was historically coloured with cinnabar — mercury sulfide (HgS), the very ore from which the metal itself is roasted out.
History & name
Mercury has been known since antiquity: Egyptian tombs from about 1500 BCE preserve vials of it, and alchemists prized the “living silver” as an essence of metallicity itself. The Greeks called it hydrargyros, “water-silver”, which Latin folded into hydrargyrum and chemistry into the symbol Hg; the English name honours the swift messenger god Mercury — quicksilver in plain speech. Torricelli balanced a column of it against the atmosphere in 1643 and invented the barometer, and for three centuries mercury thermometers were the world’s standard — until Minamata’s tragedy in 1950s Japan revealed the metal’s dark side and led, in 2013, to the Minamata Convention now retiring it worldwide.