Discovery of francium

Francium was discovered in 1939 by Marguerite Perey, a French physicist at the Curie Institute in Paris who had started her career as Marie Curie's laboratory assistant. While purifying a sample of actinium, she observed a faint radioactivity that she could not attribute to any known element, and she proved that it came from a new alkali metal, which she named francium after her homeland. It was the last element to be discovered in nature before the era of synthetic elements. Francium is extraordinarily rare and highly unstable, with its longest-lived isotope lasting only about twenty-two minutes, so only tiny traces exist at any time. Its properties are therefore known mostly from trace experiments, and it has no practical use outside research.

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