Definition of "americium" []

• A white metallic transuranic element of the actinide series, having isotopes with mass numbers from 237 to 246 and half-lives from 25 minutes to 7,950 years. Its longest-lived isotopes, Am 241 and Am 243, are alpha-ray emitters used as radiation sources in research. Atomic number 95; specific gravity 11.7; valence 3, 4, 5, 6. See Table at element. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "Barot wrote a letter to the leaders of al-Qaeda proposing that he would mine the small amount of radioactive material known as americium that can be found in ordinary smoke detectors and use it to build a radiological device."
• "Smoke detectors, he learned, contain small amounts of a radio-active element called americium, while camping lanterns contain thorium."
• "Hahn diligently amassed this radioactive material by collecting small amounts from household products, such as americium from smoke detectors, thorium from camping lantern mantles, radium from clocks and tritium (as neutron moderator) from gun-sights."