<P> All elements of period 7 are radioactive . This period contains the actinides, which contains the heaviest naturally occurring element, plutonium; subsequent elements must be synthesized artificially . Whilst the first five of these are now available in macroscopic quantities, most are extremely rare, having only been prepared in microgram amounts or less . The later, transactinide elements have only been identified in laboratories in batches of a few atoms at a time . </P> <P> Although the rarity of many of these elements means that experimental results are not very extensive, their periodic and group trends are less well defined than other periods . Whilst francium and radium do show typical properties of their respective groups, actinides display a much greater variety of behaviour and oxidation states than the lanthanides . These peculiarities are due to a variety of factors, including a large degree of spin - orbit coupling and relativistic effects, ultimately caused by the very high positive electrical charge from their massive atomic nuclei . </P> <Dl> <Dd> <Table> <Tr> <Th_colspan="3"> Chemical element </Th> <Th> Chemical series </Th> <Th> Electron configuration </Th> <Th> Occurrence </Th> </Tr> <Tr> <Th> </Th> <Th> </Th> <Th> </Th> <Th> </Th> <Th> </Th> <Th> </Th> </Tr> <Tr> <Td> 87 </Td> <Td> Fr </Td> <Td> Francium </Td> <Td> Alkali metal </Td> <Td> (Rn) 7s </Td> <Td> From decay </Td> </Tr> <Tr> <Td> 88 </Td> <Td> Ra </Td> <Td> Radium </Td> <Td> Alkaline earth metal </Td> <Td> (Rn) 7s </Td> <Td> From decay </Td> </Tr> <Tr> <Td> 89 </Td> <Td> Ac </Td> <Td> Actinium </Td> <Td> Actinide </Td> <Td> (Rn) 6d 7s (*) </Td> <Td> From decay </Td> </Tr> <Tr> <Td> 90 </Td> <Td> Th </Td> <Td> Thorium </Td> <Td> Actinide </Td> <Td> (Rn) 6d 7s (*) </Td> <Td> Primordial </Td> </Tr> <Tr> <Td> 91 </Td> <Td> Pa </Td> <Td> Protactinium </Td> <Td> Actinide </Td> <Td> (Rn) 5f 6d 7s (*) </Td> <Td> From decay </Td> </Tr> <Tr> <Td> 92 </Td> <Td> U </Td> <Td> Uranium </Td> <Td> Actinide </Td> <Td> (Rn) 5f 6d 7s (*) </Td> <Td> Primordial </Td> </Tr> <Tr> <Td> 93 </Td> <Td> Np </Td> <Td> Neptunium </Td> <Td> Actinide </Td> <Td> (Rn) 5f 6d 7s (*) </Td> <Td> From decay </Td> </Tr> <Tr> <Td> 94 </Td> <Td> Pu </Td> <Td> Plutonium </Td> <Td> Actinide </Td> <Td> (Rn) 5f 7s </Td> <Td> From decay </Td> </Tr> <Tr> <Td> 95 </Td> <Td> Am </Td> <Td> Americium </Td> <Td> Actinide </Td> <Td> (Rn) 5f 7s </Td> <Td> Synthetic </Td> </Tr> <Tr> <Td> 96 </Td> <Td> Cm </Td> <Td> Curium </Td> <Td> Actinide </Td> <Td> (Rn) 5f 6d 7s (*) </Td> <Td> Synthetic </Td> </Tr> <Tr> <Td> 97 </Td> <Td> Bk </Td> <Td> Berkelium </Td> <Td> Actinide </Td> <Td> (Rn) 5f 7s </Td> <Td> Synthetic </Td> </Tr> <Tr> <Td> 98 </Td> <Td> Cf </Td> <Td> Californium </Td> <Td> Actinide </Td> <Td> (Rn) 5f 7s </Td> <Td> Synthetic </Td> </Tr> <Tr> <Td> 99 </Td> <Td> Es </Td> <Td> Einsteinium </Td> <Td> Actinide </Td> <Td> (Rn) 5f 7s </Td> <Td> Synthetic </Td> </Tr> <Tr> <Td> 100 </Td> <Td> Fm </Td> <Td> Fermium </Td> <Td> Actinide </Td> <Td> (Rn) 5f 7s </Td> <Td> Synthetic </Td> </Tr> <Tr> <Td> 101 </Td> <Td> Md </Td> <Td> Mendelevium </Td> <Td> Actinide </Td> <Td> (Rn) 5f 7s </Td> <Td> Synthetic </Td> </Tr> <Tr> <Td> 102 </Td> <Td> No </Td> <Td> Nobelium </Td> <Td> Actinide </Td> <Td> (Rn) 5f 7s </Td> <Td> Synthetic </Td> </Tr> <Tr> <Td> 103 </Td> <Td> Lr </Td> <Td> Lawrencium </Td> <Td> Actinide </Td> <Td> (Rn) 5f 7s 7p (*) </Td> <Td> Synthetic </Td> </Tr> <Tr> <Td> 104 </Td> <Td> Rf </Td> <Td> Rutherfordium </Td> <Td> Transition metal </Td> <Td> (Rn) 5f 6d 7s </Td> <Td> Synthetic </Td> </Tr> <Tr> <Td> 105 </Td> <Td> Db </Td> <Td> Dubnium </Td> <Td> Transition metal </Td> <Td> (Rn) 5f 6d 7s </Td> <Td> Synthetic </Td> </Tr> <Tr> <Td> 106 </Td> <Td> Sg </Td> <Td> Seaborgium </Td> <Td> Transition metal </Td> <Td> (Rn) 5f 6d 7s </Td> <Td> Synthetic </Td> </Tr> <Tr> <Td> 107 </Td> <Td> Bh </Td> <Td> Bohrium </Td> <Td> Transition metal </Td> <Td> (Rn) 5f 6d 7s </Td> <Td> Synthetic </Td> </Tr> <Tr> <Td> 108 </Td> <Td> Hs </Td> <Td> Hassium </Td> <Td> Transition metal </Td> <Td> (Rn) 5f 6d 7s </Td> <Td> Synthetic </Td> </Tr> <Tr> <Td> 109 </Td> <Td> Mt </Td> <Td> Meitnerium </Td> <Td> Transition metal (?) </Td> <Td> (Rn) 5f 6d 7s (?) </Td> <Td> Synthetic </Td> </Tr> <Tr> <Td> 110 </Td> <Td> Ds </Td> <Td> Darmstadtium </Td> <Td> Transition metal (?) </Td> <Td> (Rn) 5f 6d 7s (?) </Td> <Td> Synthetic </Td> </Tr> <Tr> <Td> 111 </Td> <Td> Rg </Td> <Td> Roentgenium </Td> <Td> Transition metal (?) </Td> <Td> (Rn) 5f 6d 7s (?) </Td> <Td> Synthetic </Td> </Tr> <Tr> <Td> 112 </Td> <Td> Cn </Td> <Td> Copernicium </Td> <Td> Post-transition metal </Td> <Td> (Rn) 5f 6d 7s (?) </Td> <Td> Synthetic </Td> </Tr> <Tr> <Td> 113 </Td> <Td> Nh </Td> <Td> Nihonium </Td> <Td> Post-transition metal (?) </Td> <Td> (Rn) 5f 6d 7s 7p (?) </Td> <Td> Synthetic </Td> </Tr> <Tr> <Td> 114 </Td> <Td> Fl </Td> <Td> Flerovium </Td> <Td> Post-transition metal (?) </Td> <Td> (Rn) 5f 6d 7s 7p (?) </Td> <Td> Synthetic </Td> </Tr> <Tr> <Td> 115 </Td> <Td> Mc </Td> <Td> Moscovium </Td> <Td> Post-transition metal (?) </Td> <Td> (Rn) 5f 6d 7s 7p (?) </Td> <Td> Synthetic </Td> </Tr> <Tr> <Td> 116 </Td> <Td> Lv </Td> <Td> Livermorium </Td> <Td> Post-transition metal (?) </Td> <Td> (Rn) 5f 6d 7s 7p (?) </Td> <Td> Synthetic </Td> </Tr> <Tr> <Td> 117 </Td> <Td> Ts </Td> <Td> Tennessine </Td> <Td> Post-transition metal (?) </Td> <Td> (Rn) 5f 6d 7s 7p (?) </Td> <Td> Synthetic </Td> </Tr> <Tr> <Td> 118 </Td> <Td> Og </Td> <Td> Oganesson </Td> <Td> Noble gas (?) </Td> <Td> (Rn) 5f 6d 7s 7p (?) </Td> <Td> Synthetic </Td> </Tr> </Table> </Dd> </Dl> <Dd> <Table> <Tr> <Th_colspan="3"> Chemical element </Th> <Th> Chemical series </Th> <Th> Electron configuration </Th> <Th> Occurrence </Th> </Tr> <Tr> <Th> </Th> <Th> </Th> <Th> </Th> <Th> </Th> <Th> </Th> <Th> </Th> </Tr> <Tr> <Td> 87 </Td> <Td> Fr </Td> <Td> Francium </Td> <Td> Alkali metal </Td> <Td> (Rn) 7s </Td> <Td> From decay </Td> </Tr> <Tr> <Td> 88 </Td> <Td> Ra </Td> <Td> Radium </Td> <Td> Alkaline earth metal </Td> <Td> (Rn) 7s </Td> <Td> From decay </Td> </Tr> <Tr> <Td> 89 </Td> <Td> Ac </Td> <Td> Actinium </Td> <Td> Actinide </Td> <Td> (Rn) 6d 7s (*) </Td> <Td> From decay </Td> </Tr> <Tr> <Td> 90 </Td> <Td> Th </Td> <Td> Thorium </Td> <Td> Actinide </Td> <Td> (Rn) 6d 7s (*) </Td> <Td> Primordial </Td> </Tr> <Tr> <Td> 91 </Td> <Td> Pa </Td> <Td> Protactinium </Td> <Td> Actinide </Td> <Td> (Rn) 5f 6d 7s (*) </Td> <Td> From decay </Td> </Tr> <Tr> <Td> 92 </Td> <Td> U </Td> <Td> Uranium </Td> <Td> Actinide </Td> <Td> (Rn) 5f 6d 7s (*) </Td> <Td> Primordial </Td> </Tr> <Tr> <Td> 93 </Td> <Td> Np </Td> <Td> Neptunium </Td> <Td> Actinide </Td> <Td> (Rn) 5f 6d 7s (*) </Td> <Td> From decay </Td> </Tr> <Tr> <Td> 94 </Td> <Td> Pu </Td> <Td> Plutonium </Td> <Td> Actinide </Td> <Td> (Rn) 5f 7s </Td> <Td> From decay </Td> </Tr> <Tr> <Td> 95 </Td> <Td> Am </Td> <Td> Americium </Td> <Td> Actinide </Td> <Td> (Rn) 5f 7s </Td> <Td> Synthetic </Td> </Tr> <Tr> <Td> 96 </Td> <Td> Cm </Td> <Td> Curium </Td> <Td> Actinide </Td> <Td> (Rn) 5f 6d 7s (*) </Td> <Td> Synthetic </Td> </Tr> <Tr> <Td> 97 </Td> <Td> Bk </Td> <Td> Berkelium </Td> <Td> Actinide </Td> <Td> (Rn) 5f 7s </Td> <Td> Synthetic </Td> </Tr> <Tr> <Td> 98 </Td> <Td> Cf </Td> <Td> Californium </Td> <Td> Actinide </Td> <Td> (Rn) 5f 7s </Td> <Td> Synthetic </Td> </Tr> <Tr> <Td> 99 </Td> <Td> Es </Td> <Td> Einsteinium </Td> <Td> Actinide </Td> <Td> (Rn) 5f 7s </Td> <Td> Synthetic </Td> </Tr> <Tr> <Td> 100 </Td> <Td> Fm </Td> <Td> Fermium </Td> <Td> Actinide </Td> <Td> (Rn) 5f 7s </Td> <Td> Synthetic </Td> </Tr> <Tr> <Td> 101 </Td> <Td> Md </Td> <Td> Mendelevium </Td> <Td> Actinide </Td> <Td> (Rn) 5f 7s </Td> <Td> Synthetic </Td> </Tr> <Tr> <Td> 102 </Td> <Td> No </Td> <Td> Nobelium </Td> <Td> Actinide </Td> <Td> (Rn) 5f 7s </Td> <Td> Synthetic </Td> </Tr> <Tr> <Td> 103 </Td> <Td> Lr </Td> <Td> Lawrencium </Td> <Td> Actinide </Td> <Td> (Rn) 5f 7s 7p (*) </Td> <Td> Synthetic </Td> </Tr> <Tr> <Td> 104 </Td> <Td> Rf </Td> <Td> Rutherfordium </Td> <Td> Transition metal </Td> <Td> (Rn) 5f 6d 7s </Td> <Td> Synthetic </Td> </Tr> <Tr> <Td> 105 </Td> <Td> Db </Td> <Td> Dubnium </Td> <Td> Transition metal </Td> <Td> (Rn) 5f 6d 7s </Td> <Td> Synthetic </Td> </Tr> <Tr> <Td> 106 </Td> <Td> Sg </Td> <Td> Seaborgium </Td> <Td> Transition metal </Td> <Td> (Rn) 5f 6d 7s </Td> <Td> Synthetic </Td> </Tr> <Tr> <Td> 107 </Td> <Td> Bh </Td> <Td> Bohrium </Td> <Td> Transition metal </Td> <Td> (Rn) 5f 6d 7s </Td> <Td> Synthetic </Td> </Tr> <Tr> <Td> 108 </Td> <Td> Hs </Td> <Td> Hassium </Td> <Td> Transition metal </Td> <Td> (Rn) 5f 6d 7s </Td> <Td> Synthetic </Td> </Tr> <Tr> <Td> 109 </Td> <Td> Mt </Td> <Td> Meitnerium </Td> <Td> Transition metal (?) </Td> <Td> (Rn) 5f 6d 7s (?) </Td> <Td> Synthetic </Td> </Tr> <Tr> <Td> 110 </Td> <Td> Ds </Td> <Td> Darmstadtium </Td> <Td> Transition metal (?) </Td> <Td> (Rn) 5f 6d 7s (?) </Td> <Td> Synthetic </Td> </Tr> <Tr> <Td> 111 </Td> <Td> Rg </Td> <Td> Roentgenium </Td> <Td> Transition metal (?) </Td> <Td> (Rn) 5f 6d 7s (?) </Td> <Td> Synthetic </Td> </Tr> <Tr> <Td> 112 </Td> <Td> Cn </Td> <Td> Copernicium </Td> <Td> Post-transition metal </Td> <Td> (Rn) 5f 6d 7s (?) </Td> <Td> Synthetic </Td> </Tr> <Tr> <Td> 113 </Td> <Td> Nh </Td> <Td> Nihonium </Td> <Td> Post-transition metal (?) </Td> <Td> (Rn) 5f 6d 7s 7p (?) </Td> <Td> Synthetic </Td> </Tr> <Tr> <Td> 114 </Td> <Td> Fl </Td> <Td> Flerovium </Td> <Td> Post-transition metal (?) </Td> <Td> (Rn) 5f 6d 7s 7p (?) </Td> <Td> Synthetic </Td> </Tr> <Tr> <Td> 115 </Td> <Td> Mc </Td> <Td> Moscovium </Td> <Td> Post-transition metal (?) </Td> <Td> (Rn) 5f 6d 7s 7p (?) </Td> <Td> Synthetic </Td> </Tr> <Tr> <Td> 116 </Td> <Td> Lv </Td> <Td> Livermorium </Td> <Td> Post-transition metal (?) </Td> <Td> (Rn) 5f 6d 7s 7p (?) </Td> <Td> Synthetic </Td> </Tr> <Tr> <Td> 117 </Td> <Td> Ts </Td> <Td> Tennessine </Td> <Td> Post-transition metal (?) </Td> <Td> (Rn) 5f 6d 7s 7p (?) </Td> <Td> Synthetic </Td> </Tr> <Tr> <Td> 118 </Td> <Td> Og </Td> <Td> Oganesson </Td> <Td> Noble gas (?) </Td> <Td> (Rn) 5f 6d 7s 7p (?) </Td> <Td> Synthetic </Td> </Tr> </Table> </Dd>

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