10th January: Francium

The element Francium was discovered on this date in 1939. Here are some things you probably don't know about this element.

1. What is it? A highly radioactive alkaline metal.
2. It was the last element to be discovered in nature rather than made in a lab.
3. Francium was discovered by Marguerite Perey, who was a student of Marie Curie. In 1962, she was the first woman to be elected to the French Académie des Sciences, an honour Curie herself was denied.
4. The atomic number of Francium is 87 and its chemical symbol is Fr.
5. It used to be known as eka-caesium and actinium K. Perey first proposed the name catium for her newly discovered element, but this was opposed because although the name referred to cation, or positive charge, her supervisor thought it would remind people of Cats. So Perey came up with Francium instead.
6. Francium is named after France, because the element was discovered in Paris. It is one of two elements named after France, the other one being gallium.
7. In nature, it's extremely rare with only about 20–30 g (one ounce) existing in the Earth's crust at any given time. The largest amount produced in a laboratory was a cluster of more than 300,000 atoms.
8. Because it's so rare, nobody really knows what its melting point or boiling point is but scientists have come up with a best guess of 27 °C/80 °F for the melting point and 677 °C/1250 °F for the boiling point.
9. There are 34 known isotopes of francium, the most stable of which has a half-life of just 22 minutes.
10. Again because it is so rare and radioactive, it has no commercial uses. Perey hoped it might be useful as a diagnostic tool for cancer but this proved not only impractical but dangerous as the substance is carcinogenic. Perey developed bone cancer which eventually killed her.