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| actinide |
any of the chemical elements of the actinide series. |
| berkelium |
a radioactive synthetic metal element of the actinide series that has ninety-seven protons in each nucleus. (symbol: Bk) |
| neptunium |
a synthetic radioactive chemical element of the actinide series that contains ninety-three protons in each nucleus. (symbol: Np) |
| nobelium |
a synthetic radioactive chemical element of the actinide series that has 102 protons in each nucleus. (symbol: No) |
| plutonium |
a radioactive chemical element of the actinide series that has ninety-four protons in each nucleus and that is capable of explosive nuclear fission in a chain reaction, used as fuel in some types of nuclear reactors. (symbol: Pu) |
| protactinium |
a very toxic radioactive chemical element of the actinide series that has ninety-one protons in each nucleus and that is a product of the radioactive decay of uranium. (symbol: Pa) |
| thorium |
a radioactive chemical element of the actinide series that has ninety protons in each nucleus and that occurs as a malleable, lustrous, grayish white solid metal. (symbol: Th) |
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