Francium - ₈₇Fr: historical information

Francium was discovered in 1939 by Marguerite Perey of the Curie Institute in Paris, (France) but its existence was predicted by Mendeleev during the 1870's. Since its properties should track those of caesium rather closely, he called it eka-caesium. Marguerite Perey noticed an α decay product from actinium, now recognized as ²²³₈₇Fr. This is the longest-lived isotope of actinium with a half life of about 22 minutes. She called the new element Francium after her country.