(So named (Latin Neptunus, Neptune) by Edwin McMillan and Philip Abelson because it comes next to uranium, as the planet Neptune comes next to Uranus) A silver-colored, radioactive, metallic chemical element, one of the actinides, produced by bombarding uranium atoms with neutrons.

Symbol: Np
Atomic number: 93
Atomic weight: 237 (isotope with the longest known half-life)
Density (at room temperature and pressure): 20.45 g/cc
Melting point: 640°C
Boiling point: 3,902°C
Ground state electron configuration: [Rn]5f46d17s2

Neptunium
Symbol: Np
Atomic Number: 93
Atomic Weight: 237 (most stable)
Boiling Point: 4175 K
Melting Point: 912 K
Density at 300K: 20.2 g/cm3
Covalent radius: ???
Atomic radius: ???
Atomic volume: 21.1 cm3/mol
First ionization potental: 6.19 V
Specific heat capacity: ??? Jg-1K-1
Thermal conductivity: 6.3 Wm-1K-1
Electrical conductivity: 0.8*106Ω-1m-1
Heat of fusion: ??? kJ/mol
Heat of vaporization: ??? kJ/mol
Electronegativity: 1.36 (Pauling's)

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Nep*tu"ni*um (?), n. [NL.]

A new metallic element, of doubtful genuineness and uncertain indentification, said to exist in certain minerals, as columbite.

<-- a radioactive element, produced in reactors from Pt or U; At. num. = 93, Sym. Np, At. Wt. 237.0482 [MW10] -->

Hermann.

 

© Webster 1913.

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