transuranic element

A transuranic element is any element lying beyond uranium in the periodic table, i.e. any element of atomic number greater than 92. The best known transuranic elements are those in the actinide (atomic numbers 89 to 103). Neptunium was the first of the transuranic elements to be produced in 1940 by the US physicist Edward McMillan and US physical chemist Philip Abelson, who bombarded uranium with neutrons in a synchrocyclotron.


Except for the plutonium isotopes Pu-244 (half-life about 80 million years) and Pu-239 (continuous reformation in rock containing uranium by neutron capture in U-238 by neutrons from the spontaneous fission of U-238) detected in very small quantities, all transuranic elements must be produced artificially by suitable nuclear reactions, usually involving bombardment with neutrons or alpha particles. All are radioactive.


Table of transuranic elements
element name symbol atomic no.
neptunium Np 93
plutonium Pu 94
americium Am 95
curium Cm 96
berkelium Bk 97
californium Cf 98
einsteinium Es 99
fermium Fm 100
mendelevium Md 101
nobelium No 102
lawrencium Lw 103
rutherfordium Rf 104
dubnium Db 105
seaborgium Sb 106
bohrium Bh 107
hassium Hs 108
meitnerium Mt 109
darmstadtium Ds 110
roentgenium Rg 111
not yet named - 112
not yet named - 114
not yet named - 115