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