what are its data source?
CRC Handbook of Physics and Chemistry;" standard electrode potentials
Nonmetal
CRC Handbook of Physics and Chemistry;" standard electrode potentials
what is metalloid? It is a type of chemical element. what are the isotopes of this element? UNANSWERABLE what is its description? It is a  mixture of metals and nonmetals. what are the properties of the latter mentioned? Physically, they largely exist as diatomic or monatomic gases while chemically they mostly have high ionisation energies. what are its alternative categories? The relative homogeneity of the halogens, physical form, electronegativity etc
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Nonmetal [SEP] Data sources
Unless otherwise stated, melting points, boiling points, densities, crystalline structures, ionisation energies, electron affinities, and electronegativity values are from the "CRC Handbook of Physics and Chemistry;" standard electrode potentials are from the 1989 compilation by Steven Bratsch.