What is actinium? (What is transuranic elements?

•          Actinium (Z= 89) and the succeeding elements up to lawrencium (Z=103) are called Actinides.
•          The outer electronic configuration of actinium is 5f⁰6d¹7s².
•          In the succeeding fourteen elements, 14 electrons are successively added to the empty 5f subshell.
•          Thus, just as in lanthanides, the antepenultimate, 4f subshell is filled successively by the addition of one electron at a time, similarly in actinides; the antepenultimate 5f subshell is filled successively by the addition of one electron at each step.
•          Just as lanthanum is the prototype of the lanthanides, actinium is the prototype of the actinides.
•          Lanthanides constitute the first inner transition series while actinides constitute the second inner transition series.
•          Since, in these elements, the number of electrons in the outermost as well as the penultimate shell remains the same; all the actinides resemble one another very closely.
•      SOURCES OF ACTINIDES:
•          The chief source of thorium and uranium are the widely distributed thorium and uranium ores.
•          Thorium is mostly obtained from monazite sands while uranium is mostly obtained from pitchblende and carnotite.
•          Actinium and protactinium occur in all uranium ores as decay products of ²³⁵U
•        None of the elements heavier heavier than uranium occurs in nature.