Gold (Au)
“The metal that never fades — Tutankhamun’s 3,300-year-old mask still gleams, and so will a bride’s bangles after a lifetime.”
How its electrons are arranged
Computed from the aufbau principle, with known real-world exceptions applied automatically.
Characteristics
- Almost perfectly unreactive: oxygen, water and single acids leave it alone — only aqua regia, a 3:1 mix of hydrochloric and nitric acids, can dissolve it, hence the name “royal water”.
- Softness is measured in carats: pure gold is 24 carat, and jewellers stiffen it by alloying — the warm blush of 21–22 carat Bangladeshi wedding gold is the fingerprint of its copper partner.
- A relativistic metal: fast-moving inner electrons shrink the 6s orbital and swell 5d — an effect of Einstein’s physics that narrows gold’s absorption to blue light, so it reflects the golden remainder.
- Dense (19.3 g/cm³) and champion of malleability and ductility together — one gram stretches into a wire more than two kilometres long, a feat no other metal matches.
A deep yellow, heavy, soft metal — one of the very few coloured metals (copper and caesium are the others), where nearly every metal is silvery-white. It is the champion of malleability: a single gram can be beaten into a sheet one metre square, and gold leaf is beaten so thin that light passes through it green.
Where you meet it
✦ Uses
- Jewellery and wedding wealth: in Bangladesh the bride’s 21–22 carat bangles and tikli, bought by bhori, are her traditional stridhan — savings that never rust, rot or burn.
- Electronics: the bonding wires and connector contacts inside every smartphone and computer are gold, because a gold contact never oxidises and never raises its resistance.
- Medicine and dentistry: gold crowns outlast decades of chewing, and tiny gold particles colour the result line on rapid test strips, from pregnancy kits to COVID-19 antigen tests.
- National reserves: central banks, Bangladesh Bank included, hold gold bars as the crisis-proof anchor of a country’s wealth; Olympic “gold” medals, meanwhile, are silver plated with at least 6 grams of real gold.
◍ Everyday examples
- At a Bangladeshi wedding the bride’s bangles and tikli are 21–22 carat gold, weighed by the jeweller in bhori (11.66 grams) before the elders settle the bill.
- Every smartphone holds roughly 0.03 grams of gold in its circuitry — negligible in one handset, a small mine’s worth across a hundred million of them.
- Coin hoards and temple idols come out of the soil after centuries still bright — the archaeologist’s proof that gold simply waits out time.
History & name
Gold needed no discoverer: it occurs native, glinting in quartz veins and river gravels, and smiths were hammering it into ornaments at least 6,000 years ago — Tutankhamun’s funerary mask is over 3,300 years old and still untarnished. Because gold outlasts every empire, from pharaonic Egypt to the gold-minting sultans of Bengal, it became the very definition of stored wealth. The English name descends from old Germanic roots meaning “the yellow one”; the chemical symbol Au, by contrast, is borrowed from Latin aurum, kin to aurora — the glowing metal of dawn.