mesothorium

noun

meso·​thorium

¦me|zō,

¦mē|,

|sō+

: either of two radioactive products intermediate between thorium and radiothorium in the thorium series or a mixture of the two products obtained usually from thorium minerals (as monazite sand) and used as a substitute for radium especially in luminous paints:

a

: an isotope of radium

called also mesothorium 1

—symbol MsTh₁ or Ra²²⁸

b

: an isotope of actinium

called also mesothorium 2

—symbol MsTh₂ or Ac²²⁸

Word History

Etymology

New Latin, from mes- + thorium

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