Difference between revisions 489410985 and 489418376 on enwiki

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! scope="col" style="width: 1.0%;" | [[Periodic table group|Group]] #
! scope="col" style="width: 5.5%;" | [[Alkali metal|1]]
! scope="col" style="width: 5.5%;" | [[Alkaline earth metal|2]]
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* {{colorbox|{{element color/1900-1949}}}} 1900–1949 (13 elements):  development of [[old quantum theory]] and [[quantum mechanics]].
* {{colorbox|{{element color/1950-1999}}}} 1950–1999 (16 elements):  post Manhattan project; [[Synthetic element|synthesis]] of atomic numbers 98 and above ([[collider]]s, bombardment techniques).
* {{colorbox|{{element color/2000-present}}}} Since 2000 (5 elements): recent synthesis.
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