When Mendeleev first proposed his periodic table in 1869 he left gaps for elements not yet discovered, but that he predicted should exist. One such gap was one beneath caesium, a position later found ...

It was recognized early on that the periodic table more or less fizzles out after ... Estimates suggest that there is only about 30 g of francium in the whole of the Earth's crust.

Gethin: Francium. That's not an element that you ... and are placed in the first vertical column on the left of the periodic table. All the Group 1 elements are very reactive, and all react ...