98Cf

Californium

Actinidesolidblock f

A synthetic actinide that works as a portable neutron source, one microgram emitting millions of neutrons a second for oil-well logging.

Atomic number	98
Mass number (longest-lived isotope)	251 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] 5f¹⁰ 7s²

About Californium

Californium-252 decays 3 % of the time by spontaneous fission rather than alpha emission, producing 2.3 × 10⁶ neutrons per second per microgram — a neutron source the size of a pencil lead that needs no accelerator and no reactor. That makes it the standard tool for neutron activation analysis, for start-up sources in reactors, for scanning cargo and luggage, and above all for well logging, where a probe lowered into a borehole reads back the hydrogen content and therefore the oil and water saturation of the surrounding rock. It is among the most expensive substances on Earth at roughly $27 million per gram, and world production is a few grams a year from Oak Ridge and Dimitrovgrad combined.

Use 251 g/mol in these solvers

Moles from Mass (n = m/M)

n = \frac{m}{M}

Opens with M = 251 g/mol already filled in

Gas Density from Molar Mass

\rho = \frac{PM}{RT}

Opens with M = 251 g/mol already filled in

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

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

Opens with M = 251 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 = 251 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 = 251 g/mol already filled in

← 97 BerkeliumPeriodic table99 Einsteinium →