Barium (Ba)
“A metal so poisonous it kills rats — yet doctors pour its sulfate straight down patients’ throats to photograph the gut on X-ray.”
How its electrons are arranged
Computed from the aufbau principle, with known real-world exceptions applied automatically.
The notes
Characteristics
- Electron configuration [Xe] 6s² — two valence electrons over a xenon core; Period 6, Group 2, the last stable member of the alkaline-earth family.
- Reacts eagerly with water, though less violently than its Group 1 neighbour caesium, fizzing out hydrogen gas and leaving strongly alkaline Ba(OH)₂ behind.
- Every soluble barium compound is poisonous — barium carbonate is a classic rat poison — yet BaSO₄ is so insoluble that the body simply cannot absorb it.
- Barium compounds paint a flame apple-green — the signature green of fireworks and signal flares comes from barium salts.
A soft, silvery-white metal that gleams like polished tin for a moment after cutting, then dulls to grey within minutes as air attacks the fresh face. It is heavier than such a reactive metal has any right to be — about 3.5 g/cm³ — and it fizzes in water, so it lives under oil in the chemistry store.
Where you meet it
✦ Uses
- The “barium meal”: a chalky BaSO₄ milkshake swallowed before an X-ray coats the stomach and intestines, making the whole digestive tract stand out white on the film.
- Barite (BaSO₄) drilling mud — its enormous density tames high-pressure oil and gas zones in deep wells, including the wells drilled for Bangladesh’s gas fields.
- Green fireworks and emergency flares: barium nitrate and barium chlorate supply the vivid green stars that burst at weddings and celebrations.
- Barium metal as a “getter” inside old television tubes and valves — a pinch of it swallows stray gas molecules, keeping the vacuum perfect for life.
◍ Everyday examples
- Any relative sent for a barium-meal X-ray at a diagnostic centre in Dhaka or Chattogram has safely drunk barium sulfate.
- The green bursts in Eid or wedding-night fireworks are barium compounds burning in the sky overhead.
- An old CRT television set in a scrap shop once carried its barium getter, silently guarding the vacuum that made the picture possible.
History & name
Around 1602 the Italian shoemaker and alchemist Vincenzo Casciarolo found a strange heavy stone near Bologna that glowed in the dark after a day in the sunshine — the famous “Bologna stone”, in reality barium sulfate. In 1774 Carl Wilhelm Scheele showed that the stone’s earth, baryta, matched no known substance, and in 1808 Humphry Davy finally isolated the metal itself by electrolysis. The Greek barys, “heavy”, gave the element its name — honest praise for a stone startlingly dense at 4.5 g/cm³.