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technetium

(Encyclopedia)technetium tĕknēˈshēəm [key] [Gr. technetos=artificial], artificially produced radioactive chemical element; symbol Tc; at. no. 43; mass no. of most stable isotope 98; m.p. 2,200℃; b.p. 4,877�...

group

(Encyclopedia)group, in mathematics, system consisting of a set of elements and a binary operation a∘b defined for combining two elements such that the following requirements are satisfied: (1) The set is closed ...

nobelium

(Encyclopedia)nobelium nōbēˈlēəm [key], artificially produced radioactive chemical element; symbol No; at. no. 102; mass no. of most stable isotope 259; m.p. 827℃; b.p. and density unknown; valence +2, +3. I...

nihonium

(Encyclopedia)nihonium nĭhōˈnēəm [key], artificially produced radioactive chemical element; symbol Nh; at. no. 113; mass number of most stable isotope 284; m.p., b.p., sp. gr., and valence unknown. Situated in...

Anaximenes

(Encyclopedia)Anaximenes ănˌəksĭmˈĭnēz [key], Greek philosopher, 6th cent. b.c., last of the Milesian school founded by Thales. With Thales he held that a single element lay behind the diversity of nature, a...

promethium

(Encyclopedia)promethium prōmēˈthēəm [key], artificially produced radioactive chemical element; symbol Pm; at. no. 61; mass no. of most stable isotope 145; m.p. 1,042℃; b.p. 3,000℃ (estimated); sp. gr. unk...

rutherfordium

(Encyclopedia)rutherfordium rŭᵺˌərfôrˈdēəm [key], artificially produced radioactive chemical element; symbol Rf; at. no. 104; mass number of most stable isotope 265; m.p., b.p., and sp. gr. unknown; valenc...

potentiometer

(Encyclopedia)potentiometer. 1 Manually adjustable, variable, electrical resistor. It has a resistance element that is attached to the circuit by three contacts, or terminals. The ends of the resistance element are...

hahnium

(Encyclopedia)hahnium hänˈēəm [key], symbol Ha, former suggested name for both element 105, now called dubnium, and element 108, now called hassium. ...

nielsbohrium

(Encyclopedia)nielsbohrium nēlzbôrˈēəm [key], symbol Ns, former suggested name for both element 105, now called dubnium, and element 107, now called bohrium. ...