Englishfor English speakers
actinium
Noun
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Actinium is a radioactive element with an atomic number of 89 and symbol Ac.
isotope
Noun
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Isotopes are atomic cores belonging to the same element that have the same number of protons, but have a different number of neutrons.
Uranium 235 and uranium 238 are isotopes of uranium.
Deutherium is an isotope of oxygen that has two neutrons.