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periodic table
periodic table chart of the elements arranged according to the periodic law discovered by Dmitri I. Mendeleev and revised by Henry G. J. Moseley . In the periodic table the elements are arranged in columns and rows according to increasing atomic number (see the table entitled Periodic Table...
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alkali metals
alkali metals metals found in Group 1 of the periodic table . Compared to other metals they are soft and have low melting points and densities. Alkali metals are powerful reducing agents and form univalent compounds. All react violently with water, releasing hydrogen and forming hydroxides. They t...
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alkaline-earth metals
alkaline-earth metals metals constituting Group 2 of the periodic table . Generally, they are softer than most other metals, react readily with water (especially when heated), and are powerful reducing agents, but they are exceeded in each of these properties by the corresponding alkali metal. The...
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Johannes Robert Rydberg
Johannes Robert Rydberg , 1854-1919, Swedish physicist. Rydberg was a professor at Lund from 1901 to 1919. He is best known for his grouping of the frequencies of certain lines of the emission spectra of the elements into simple series characterized by a running integer and a universal "Rydberg" ...
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cemetery
cemetery name used by early Christians to designate a place for burying the dead. First applied in Christian burials in the Roman catacombs , the word cemetery came into general usage in the 15th cent. Group burials have been found in Paleolithic caves, and fields of prehistoric grave mounds, or...
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Apostle Islands
Apostle Islands group of more than 20 wooded islands, in Lake Superior, off N Wis. Madeline, 13 mi (21 km) long, is the largest island and has the group's only settlement, La Pointe. Noted for their wave-eroded cliffs and abundant wildlife, the islands are visited by tourists and hunters. The islan...
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argon
argon [Gr.,=inert], gaseous chemical element; symbol Ar; at. no. 18; at. wt. 39.948; m.p. -189.2°C; b.p. -185.7°C; density 1.784 grams per liter at STP ; valence 0. Argon is a colorless, odorless, tasteless gas occurring in air (of which it constitutes 0.94% by volume) and in some volcanic...
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inert gas
inert gas or noble gas, any of the elements in Group 18 of the periodic table . In order of increasing atomic number they are: helium , neon , argon , krypton , xenon , and radon . They are colorless, odorless, tasteless gases and were once believed to be entirely inert, i.e., forming no...
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transition elements
transition elements or transition metals, in chemistry, group of elements characterized by the filling of an inner d electron orbital as atomic number increases. This includes the elements from titanium to copper, and those lying in the columns below them in the periodic table . Many of the ...
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metal
metal chemical element displaying certain properties by which it is normally distinguished from a nonmetal, notably its metallic luster, the capacity to lose electrons and form a positive ion , and the ability to conduct heat and electricity. The metals comprise about two thirds of the known ele...
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