Neptunium Np (Element 93) of Periodic Table

92 Np Neptunium

Appearance:  Silvery metallic

Mass number: 237

Atomic weigth:  237.0482 g/mol

Atomic number (Z):  93

Electrons: 93

Protons: 93

Neutrons: 146

Period: 7

Block:  f

Element category:  Actinide

Electrons per shell:  K2, L8, M18, N32, O22, P9, Q2

Electron configuration:  1s22s22p63s23p63d104s24p64d105s25p64f145d106s26p65f46d1 7s2

Phase:  Solid

Melting point:  912±3 K (639±3 oC)

Boiling point:  4447 K (4174 oC)

Density:  20.45 g/cm3

Half Life (s):  6766×1010

Lifetime (s):  9761×1010

Decay mode:  α decay

Neutron cross section (Barns): 180

Heat of fusion:  5.19 kJ/mol

Heat of vaporization:  336 kJ/mol

Molar heat capacity:  29.46 J/(mol∙K)

Molar volume:  0.000011589 m3/mol

Thermal conductivity (W/m*K):  6

Oxidation states: 7, 6, 5, 4, 3, 2

Electronegativity:  Pauling scale: 1.36

Ionization energies: 1st: 604.5 kJ/mol

Atomic radius: empirical: 155 pm

Covalent radius:  190±1 pm

Crystal structure:  Orthorhombic

Grid parameters:  a=6.663, b=4.723, c=4.887

Thermal conductivity:  6.3 W/(m∙k)

Electrical conductivity:  830000 s/m

Electrical resistivity: 1.220 μΩ∙m

Magnetic ordering:  Paramagnetic

CAS Number:  7439-99-8

Naming:  After planet Neptune

Discovery:  Edwin McMillan and Philip H. Abelson (1940)

Isotopes:  235Np 236Np 237Np 239Np

Uses:  Neptunium is little used outside research. The isotope neptunium-237 has been used in neutron detectors.

Biological role:  It is toxic due to its radioactivity.

Natural abundance:  Neptunium is obtained as a by-product from nuclear reactors. It is extracted from the spent uranium fuel rods.


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