89Ac

Actinium

Actinidesolidblock f

The head of the actinide series, radioactive enough to glow pale blue in the dark, and now aimed at tumours as a targeted alpha therapy.

Atomic number	89
Mass number (longest-lived isotope)	227 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] 6d¹ 7s²

About Actinium

Actinium mirrors lanthanum exactly, including the anomaly: no 5f electron at all, just [Rn] 6d¹ 7s², which is again why some tables start the f-block at thorium instead. André Debierne found it in the Curies' pitchblende residues in 1899, and it is about 150 times more radioactive than radium — intense enough that the surrounding air ionises and glows. Actinium-225 has become one of the most sought-after isotopes in medicine: attached to a tumour-targeting antibody or peptide, its four-alpha decay chain deposits enormous energy within a few cell diameters, and early results in metastatic prostate cancer have been striking. World supply is on the order of a single gram a year, which is the field's binding constraint.

Use 227 g/mol in these solvers

Moles from Mass (n = m/M)

n = \frac{m}{M}

Opens with M = 227 g/mol already filled in

Gas Density from Molar Mass

\rho = \frac{PM}{RT}

Opens with M = 227 g/mol already filled in

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

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

Opens with M = 227 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 = 227 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 = 227 g/mol already filled in

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