Glenn Seaborg reordered the Periodic Table- put the actinide series below the lanthanide series. (9h 26min, jan 1, 1940 y – 0h 3min, dec 31, 1940 y)
Description:
Actinide- Atomic numbers from 89-103. 15 elements, named after Actinium, first element in series. Used in nuclear reactors and bombs.Lanthanide- Atomic numbers from 57-71. 15 metals, rare earth elements. Silvery-white metals, similar to Lanthanum, first element in group. Found naturally on Earth.
"Inner Transition Elements". Rare elements listed at bottom of Periodic Table.
Added to timeline:
Date:
9h 26min, jan 1, 1940 y
0h 3min, dec 31, 1940 y
~ 12 months