actinide

Meanings

Plural: actinides

Noun

• any of a series of radioactive elements with atomic numbers 89 through 103
• 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.
• 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).
• (dated) 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).

Synonyms

actinoid, actinon

Related Words

actinium, americium, berkelium, californium, curium, einsteinium, fermium, lawrencium, mendelevium, neptunium, nobelium, plutonium, protactinium, thorium, uranium