(n)the order of an element in Mendeleyev's table of the elements; equal to the number of protons in the nucleus or electrons in the neutral state of an atom of an element
(n)a very poisonous metallic element that has three allotropic forms; arsenic and arsenic compounds are used as herbicides and insecticides and various alloys; found in arsenopyrite and orpiment and realgar, Syn.atomic number 33, As
(n)a heavy brittle diamagnetic trivalent metallic element (resembles arsenic and antimony chemically); usually recovered as a by-product from ores of other metals, Syn.Bi, atomic number 83
(n)a white metallic element that burns with a brilliant light; the fifth most abundant element in the earth's crust; an important component of most plants and animals, Syn.atomic number 20, Ca
(n)an abundant nonmetallic tetravalent element occurring in three allotropic forms: amorphous carbon and graphite and diamond; occurs in all organic compounds, Syn.atomic number 6, C
(n)a ductile grey metallic element of the lanthanide series; used in lighter flints; the most abundant of the rare-earth group, Syn.Ce, atomic number 58
(n)a soft silver-white ductile metallic element (liquid at normal temperatures); the most electropositive and alkaline metal, Syn.Cs, caesium, atomic number 55
(n)a common nonmetallic element belonging to the halogens; best known as a heavy yellow irritating toxic gas; used to purify water and as a bleaching agent and disinfectant; occurs naturally only as a salt (as in sea water), Syn.Cl, atomic number 17
(n)a ductile malleable reddish-brown corrosion-resistant diamagnetic metallic element; occurs in various minerals but is the only metal that occurs abundantly in large masses; used as an electrical and thermal conductor, Syn.atomic number 29, Cu
(n)a nonmetallic univalent element belonging to the halogens; usually a yellow irritating toxic flammable gas; a powerful oxidizing agent; recovered from fluorite or cryolite or fluorapatite, Syn.atomic number 9, F
(n)a rare silvery (usually trivalent) metallic element; brittle at low temperatures but liquid above room temperature; occurs in trace amounts in bauxite and zinc ores, Syn.Ga, atomic number 31
(n)a brittle grey crystalline element that is a semiconducting metalloid (resembling silicon) used in transistors; occurs in germanite and argyrodite, Syn.atomic number 32, Ge
(n)a soft yellow malleable ductile (trivalent and univalent) metallic element; occurs mainly as nuggets in rocks and alluvial deposits; does not react with most chemicals but is attacked by chlorine and aqua regia, Syn.Au, atomic number 79
(n)a grey tetravalent metallic element that resembles zirconium chemically and is found in zirconium minerals; used in filaments for its ready emission of electrons, Syn.atomic number 72, Hf
(n)a very light colorless element that is one of the six inert gasses; the most difficult gas to liquefy; occurs in economically extractable amounts in certain natural gases (as those found in Texas and Kansas), Syn.atomic number 2, He
(n)a nonmetallic univalent element that is normally a colorless and odorless highly flammable diatomic gas; the simplest and lightest and most abundant element in the universe, Syn.atomic number 1, H
(n)a nonmetallic element belonging to the halogens; used especially in medicine and photography and in dyes; occurs naturally only in combination in small quantities (as in sea water or rocks), Syn.I, atomic number 53, iodin
(n)a heavy ductile magnetic metallic element; is silver-white in pure form but readily rusts; used in construction and tools and armament; plays a role in the transport of oxygen by the blood, Syn.Fe, atomic number 26
(n)a white soft metallic element that tarnishes readily; occurs in rare earth minerals and is usually classified as a rare earth, Syn.atomic number 57, La