Actinide
/ˈæktɪnaɪd/ noun
noun ·Rare ·Advanced level
Definitions
Noun
- 1 Any of the 15 radioactive elements of the periodic table from actinium to lawrencium that are positioned under the lanthanides, to which they have similar chemistry.
- 2 any of a series of radioactive elements with atomic numbers 89 through 103 wordnet
- 3 Any of the 14 elements from actinium to nobelium (lawrencium is excluded by some authors as it is a d-block rather than an f-block element).
- 4 Any of the 14 elements from thorium to lawrencium (actinium having been mistakenly excluded because it was thought to be a d-block element in the past). dated
Synonyms
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More examples"Einsteinium is the name for the element with atomic number 99 and is represented by the symbol Es. It is a member of the actinide group."
Etymology
From actin- + -ide.