93Np

Neptunium

Actinidesolidblock f

The first transuranic element, made at Berkeley in 1940 and named for the planet beyond Uranus, just as uranium was named for Uranus itself.

Atomic number	93
Mass number (longest-lived isotope)	237 g/mol
This element has no stable isotope, so it has no standard atomic weight. The figure above is the mass number of its longest-lived isotope — a convention, not a measurement of a natural mixture.
Group · period	f-block series · 7
Electron configuration	[Rn] 5f⁴ 6d¹ 7s²

About Neptunium

McMillan and Abelson made neptunium in 1940 by bombarding uranium with neutrons and watching the product beta-decay into something with one more proton — the first demonstration that the periodic table did not stop at 92, and the discovery that opened the transuranic era. The naming followed the solar system outward: uranium for Uranus, then neptunium, then plutonium. Neptunium-237 has a 2.14-million-year half-life and is produced in quantity in every power reactor, which makes it one of the more troublesome components of long-term waste; it is also fissile enough that its accumulation is a proliferation concern. A pure neptunium sphere has a critical mass of about 60 kg, a fact declassified only in 2002.

Use 237 g/mol in these solvers

Moles from Mass (n = m/M)

n = \frac{m}{M}

Opens with M = 237 g/mol already filled in

Gas Density from Molar Mass

\rho = \frac{PM}{RT}

Opens with M = 237 g/mol already filled in

Faraday's Law of Electrolysis (m = QM/nF)

m = \frac{Q M}{n F}

Opens with M = 237 g/mol already filled in

Ion Concentration as CaCO₃ Equivalent

C_{\mathrm{CaCO_3}} = C_{\mathrm{ion}} \times \frac{50.04}{\mathrm{EW}}

Opens with EW = 237 g/mol already filled in

Acid Feed to Reduce Alkalinity

\dot m = \frac{\Delta \mathrm{Alk} \, Q \times \frac{\mathrm{EW}}{50.04}}{p/100\%}

Opens with EW = 237 g/mol already filled in

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