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Ha,formerly the suggested symbol for the name hahnium, which was applied variously to two elements, now called dubniumdubnium
, artificially produced radioactive chemical element; symbol Db; at. no. 105; mass number of most stable isotope 268; m.p., b.p., and sp. gr. unknown; valence +5.
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, artificially produced radioactive chemical element; symbol Hs; at. no. 108; mass number of most stable isotope 277; m.p., b.p., sp. gr., and valence unknown. Situated in Group 8 of the periodic table, it is expected to have properties similar to those of osmium.
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HAAbbrev. for hour angle.