Americium.

Americium (ămərĭ′shēəm), artificially produced radioactive chemical element; symbol Am; at. no. 95; mass no. of most stable isotope 243; m.p. about 1,175C°; b.p. about 2,600C°; sp. gr. 13.67 at 20C°; valence +2, +3, +4, +5, or +6. Americium is a silver-white metal thought to have either a loose-packed cubic or a close-packed double hexagonal crystalline structure. The pure metal has been prepared by reduction of americium trifluoride with barium vapor at about 1,100C°. It tarnishes slowly in dry air. [ABSTRACT FROM PUBLISHER]

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