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Properties of substance:
neptunium alpha form
Group of substances:
inorganic
Physical appearance:
rhombic metal
Empirical formula (Hill's system for organic substances):
Np
Structural formula as text:
Np
Molar/atomic mass: 237.05
Melting point (°C):
637
Boiling point (°C):
4100
Solubility (g/100 g of solvent):
water
: insoluble [
Ref.
]
Numerical data:
Year of discovery: 1940
Density:
20.45 (25°C, g/cm
3
)
Half-life:
226
93
Np = 35 ms (α (100%))
227
93
Np = 510 ms (α (about 100%))
228
93
Np = 61.4 s (electron capture (60%), α (40%), β
+
spontaneous fission (0.012%))
229
93
Np = 4 min (α (> 50%), β
+
)
230
93
Np = 4.6 min (β
+
(> 97%), α)
231
93
Np = 48.8 min (β
+
(98%), α (2%))
232
93
Np = 14.7 min (β
+
(about 100%), α (0.003%))
233
93
Np = 36.2 min (β
+
(about 100%), α)
234
93
Np = 4.4 d (β
+
(100%))
235
93
Np = 396.1 d (electron capture (about 100%), α (0.0026%))
236
93
Np = 154 000 y (electron capture (87.3%), β
-
(12.5%), α (0.16%))
236m
93
Np = 22.5 h (electron capture (52%), β
-
(48%))
237
93
Np = 2 144 000 y (α (about 100%), spontaneous fission (< 0.000 000 000 2%), heavy cluster emission
30
Mg (< 0.000 000 000 004%))
238
93
Np = 2.117 d (β
-
(100%))
238m
93
Np = 112 ns (spontaneous fission (about 100%))
239
93
Np = 2.356 d (β
-
(about 100%))
240
93
Np = 61.9 min (β
-
(100%))
240m
93
Np = 7.22 min (β
-
(about 100%), internal transition (0.11%))
241
93
Np = 13.9 min (β
-
(100%))
242
93
Np = 2.2 min (β
-
(100%))
242m
93
Np = 5.5 min (β
-
(100%))
243
93
Np = 1.85 min (β
-
(100%))
244
93
Np = 2.29 min (β
-
(100%))
Electrode potential:
Np
3+
+ 3e
-
→ Np, E = -1.856 V (water, 25°C)
Standard molar enthalpy (heat) of formation Δ
f
H
0
(298.15 K, kJ/mol):
0 (s)
Standard molar Gibbs energy of formation Δ
f
G
0
(298.15 K, kJ/mol):
0 (s)
Standard molar entropy S
0
(298.15 K, J/(mol·K)):
50.6 (s)
Molar heat capacity at constant pressure C
p
(298.15 K, J/(mol·K)):
29.5 (s)
Enthalpy (heat) of vaporization Δ
vap
H (kJ/mol):
5.2
ΔH
sublimation
(kJ/mol):
422
Standard molar enthalpy (heat) of formation Δ
f
H
0
(298.15 K, kJ/mol):
464 (g)
Standard molar entropy S
0
(298.15 K, J/(mol·K)):
197.6 (g)
Molar heat capacity at constant pressure C
p
(298.15 K, J/(mol·K)):
20.8 (g)
References:
Гурвич Я.А. Справочник молодого аппаратчика-химика. - М.: Химия, 1991. - pp. 51 [Russian]
Ефимов А.И. и др. Свойства неорганических соединений. Справочник. - Л.: Химия, 1983. - pp. 170-171 [Russian]
Михайлов В.А. Аналитическая химия нептуния. - М.: Наука, 1971. - pp. 13 [Russian]
Рабинович В.А., Хавин З.Я. Краткий химический справочник. - Л.: Химия, 1977. - pp. 86 [Russian]
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© Collected Ruslan Anatolievich Kiper, burewestnik@mail.ru
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