francium
/ˈfransɪəm
/noun [mass noun]
The chemical element of atomic number 87, a radioactive member of the alkali metal group. Francium occurs naturally as a decay product in uranium and thorium ores. (Symbol: Fr) Along the way, these disintegration series produce radioactive isotopes of protactinium, thorium, actinium, radium, francium, radon, astatine, polonium, bismuth, lead, thallium and mercury....
- Along the road to bismuth, a number of extremely high energy or otherwise dangerous alpha emitters will be present in the sample in small quantities: radium, actinium, thorium, francium, pollonium and radioactive lead, among others.
- These elements - lithium, sodium, potassium, rubidium, cesium and francium - all react with water to give solutions that change the color of a vegetable dye from red to blue.
Origin
1940s: from France (the discoverer's native country) + -ium.