The Histories Hidden in the Periodic Table

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The naming of elements No. 100 and No. 101, fermium and mendelevium, had caused little stir, but that relative calm soon shattered. In a period now called the “transfermium wars,” the cycle of discovery and doubt became the leitmotif of Cold War element research. Americans named element No. 104 after Ernest Rutherford, the father of nuclear science; the Soviets named it after Igor Kurchatov, the father of Russian nukes. To measure the number of atoms in a sample you will figure out how many moles the sample element contains. For each element the atomic weight is on the periodic table right under the symbol of the element. The carbon atomic weight is 12 units of atomic mass , so the weight of one mole is 12 grams. The number of protons in the nucleus is called the atomic number. The combined number of protons and neutrons in an atom is called the atomic mass number. This is because some elements have a different number of neutrons in the nucleus. Versions of an element with different atomic mass numbers are called isotopes. A group is a column of elements in the periodic table of the chemical elements. The elements in a group have similar physical or chemical characteristics of the outermost electron shells of their atoms. It has a bright silvery metallic luster and is one of the more reactive rare earth metals. Natural neodymium is a mixture of seven stable isotopes, though 14 other radioactive isotopes exist. Carbon is found free in nature in the forms of graphite, diamond, and fullerenes. Lanthanides make up the 15 metallic chemical elements with atomic numbers 57 through 71. Called lanthanides because they are chemically similar to lanthanum, these elements and the actinides form the category of rare earth elements. Despite this moniker, these chemicals are fairly abundant in the Earth’s crust.

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