A

David

Darling

actinide

An actinide is any member of the series of elements with atomic numbers from 89 (actinium) to 103 (lawrencium). The actinides are, in order of increasing atomic number: actinium, thorium, protactinium, uranium, neptunium, plutonium, americium, curium, berkelium, californium, einsteinium, fermium, mendelevium, nobelium, and lawrencium (see table below). Each actinide is analogous to the corresponding member of the lanthanide series. They are separated by ion-exchange chromatography.

 

The elements through uranium occur in nature; except actinium, they show valences higher than +3. The transuranic elements are synthetic; the +3 valence state becomes progressively more stable, and higher valences less stable.

 

Actinides
element Z outermost
electrons
valences
actinium (Ac) 89 6d17s2 3
thorium (Th) 90 6d27s2 4
protactinium (Pa) 91 5f26d17s2 4, 5
uranium (U) 92 5f36d17s2 3, 4, 5, 6
neptunium (Np) 93 5f46d17s2 3, 4, 5, 6, 7
plutonium (Pu) 94 5f67s2 3, 4, 5, 6, 7
americium (Am) 95 5f77s2 3, 4, 5, 6
curium (Cm) 96 5f76d17s2 3, 4
berkelium (Bk) 97 5f97s2 3, 4
californium (Cf) 98 5f107s2 2, 3
einsteinium (Es) 99 5f117s2 2, 3
fermium (Es) 100 5f127s2 2, 3
mendelevium (Md) 101 5f137s2 2, 3
nobelium (No) 102 5f147s2 2, 3
lawrencium (Lr) 103 5f146d17s2 3

 




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