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Understanding the element
Actinium (Ac) is chemical element 89. It belongs to the actinoids, and its reference state at room temperature is a solid. Those basic facts are a useful starting point for its chemistry and applications.
Where do we encounter it?
In practice, it turns up most often in scientific research and neutron sources.
scientific researchneutron sources
Standard atomic weightNo standard atomic weight
What its position in the table tells us
Actinium sits in period 7, group 3 and the D block. That location is useful because neighbouring elements often share trends in valence electrons, oxidation states and bonding behaviour.
Worth remembering
Actinium is radioactive, so its chemistry cannot be separated from nuclear physics and radiation safety
Actinium is radioactive, so its chemistry cannot be separated from nuclear physics and radiation safety