thorium /tho·ri·um/ (thor´e-um) chemical element, at. no. 90, symbol Th.
thorium (Th)
tho·ri·um (thôr  - m)n. Symbol Th1 A radioactive metallic element that is used in magnesium alloys; its longest-lived isotope, Th 232, has a half-life of 1.41 × 1010 years. Atomic number 90. |
thorium (Th)
[thôr′ē·əm]
Etymology: ONorse, Thor, god of thunder
a heavy grayish radioactive metallic element. Its atomic number is 90, and its atomic mass (weight) is 232.04. Thorium is used in nuclear medicine and in radiation therapy.
thorium
a chemical element, atomic number 90, atomic weight 232.038, symbol Th. See Table 6. Formerly used as a radiographic contrast medium.
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