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QUICK REFERENCE Symbol: Pu Atomic Number: 94 Atomic Weight: [244] Element Classification: Actinide Discovered By: Glenn T. Seaborg, Arthur Wahl, Joseph W. Kennedy, and Edwin McMillan Discovery Date: 1940 Name Origin: Named after the planet Pluto, following the pattern of naming elements after planets (like uranium for Uranus and neptunium for Neptune) Density(g/cc): 19.86 Melting […] More

QUICK REFERENCE Symbol: Np Atomic Number: 93 Atomic Weight: [237] Element Classification: Actinide Discovered By: Edwin McMillan and Philip H. Abelson Discovery Date: 1940 Name Origin: Named after the planet Neptune, following the pattern of uranium (named after Uranus) and plutonium (named later, after Pluto) Density(g/cc): 20.45 Melting Point: 644°C Boiling Point: 4000°C (estimated) Appearance: […] More

QUICK REFERENCE Symbol: U Atomic Number: 92 Atomic Weight: 238.02891 Element Classification: Actinide Discovered By: Martin Heinrich Klaproth Discovery Date: 1789 Name Origin: Named after the planet Uranus, which had been discovered eight years earlier by William Herschel Density(g/cc): 19.1 Melting Point: 1135°C Boiling Point: 4131°C Appearance: Silvery-gray metallic; it tarnishes to a dark gray […] More

QUICK REFERENCE Symbol: Pa Atomic Number: 91 Atomic Weight: 231.03588 Element Classification: Actinide Discovered By: Kasimir Fajans and Oswald Helmuth Göhring; independently by Frederick Soddy and John Cranston Discovery Date: 1913 (discovery of isotope Protactinium-234), 1917 (discovery of isotope Protactinium-231) Name Origin: From the Greek ‘protos’ meaning first and ‘actinium’, meaning “parent of actinium”, as […] More

QUICK REFERENCE Symbol: Th Atomic Number: 90 Atomic Weight: 232.03806 Element Classification: Actinide Discovered By: Jöns Jacob Berzelius Discovery Date: 1828 Name Origin: Named after Thor, the Norse god of thunder Density(g/cc): 11.7 Melting Point: 1750°C Boiling Point: 4788°C Appearance: Silvery, often with a black tarnish when exposed to air Atomic Radius(pm): 180 Discovery Thorium […] More

QUICK REFERENCE Symbol: Ac Atomic Number: 89 Atomic Weight: 227 Element Classification: Actinide Discovered By: Friedrich Oskar Giesel Discovery Date: Independently discovered by Friedrich Oskar Giesel in 1902 and by André-Louis Debierne in 1899, but Debierne is often credited with the discovery. Name Origin: From the Greek ‘aktinos’, meaning ray or beam, referring to its […] More

QUICK REFERENCE Symbol: Ra Atomic Number: 88 Atomic Weight: 226 Element Classification: Alkaline Earth Metal Discovered By: Marie Curie and Pierre Curie Discovery Date: 1898 Name Origin: From the Latin ‘radius’, meaning ray, in reference to its radioactive properties Density(g/cc): 5.5 Melting Point: 700°C Boiling Point: 1737°C Appearance: Silvery-white metallic; it is luminescent, turning black […] More

QUICK REFERENCE Symbol: Fr Atomic Number: 87 Atomic Weight: [223] Element Classification: Alkali Metal Discovered By: Marguerite Perey Discovery Date: 1939 Name Origin: Named after France, the country of its discovery Density(g/cc): Estimated to be around 1.87 (predicted) Melting Point: 27°C (estimated) Boiling Point: 677°C (estimated) Appearance: Presumed to be a highly radioactive metal; actual […] More

QUICK REFERENCE Symbol: Rn Atomic Number: 86 Atomic Weight: [222] Element Classification: Noble Gas Discovered By: Friedrich Ernst Dorn Discovery Date: 1900 Name Origin: Derived from radium; originally called “radium emanation” Density(g/cc): 0.00973 (gas at 0°C, 1 atm) Melting Point: -71°C Boiling Point: -61.7°C Appearance: Colorless gas under standard conditions Atomic Radius(pm): Estimated to be […] More

QUICK REFERENCE Symbol: At Atomic Number: 85 Atomic Weight: [210] Element Classification: Halogen Discovered By: Dale R. Corson, Kenneth Ross MacKenzie, and Emilio Segrè Discovery Date: 1940 Name Origin: Greek: ‘astatos’ (unstable) Density(g/cc): Estimated to be around 7 (predicted) Melting Point: 302°C (estimated) Boiling Point: 337°C (estimated) Appearance: Likely to be a solid under standard […] More

QUICK REFERENCE Symbol: Po Atomic Number: 84 Atomic Weight: [209] Element Classification: Metalloid Discovered By: Marie Curie and Pierre Curie Discovery Date: 1898 Name Origin: Named after Poland, the native country of Marie Curie Density(g/cc): 9.196 (calculated) Melting Point: 254°C Boiling Point: 962°C Appearance: Silvery-gray metal Atomic Radius(pm): 135 (estimated) Discovery Polonium was discovered in […] More

QUICK REFERENCE Symbol: Bi Atomic Number: 83 Atomic Weight: 208.98040 Element Classification: Post-transition Metal Discovered By: Known to alchemists since at least the 15th century Discovery Date: Recognized as a distinct element by Claude François Geoffroy in 1753 Name Origin: German: ‘Weisse Masse’ meaning white mass; later changed to ‘Bismuth’ by Kaspar Neumann Density(g/cc): 9.78 […] More