79Au

Gold

Transition metalsolidblock d

The metal that never tarnishes, dense enough to pan out of river gravel, and beaten thin enough to gild a dome at a hundred nanometres.

Atomic number	79
Standard atomic weight	196.97 g/mol ± 0.01
Group · period	11 · 6
Electron configuration	[Xe] 4f¹⁴ 5d¹⁰ 6s¹

About Gold

Gold is yellow because of relativity. Its 6s electrons move fast enough — a substantial fraction of the speed of light — that relativistic contraction pulls the 6s level down and pushes 5d up, narrowing the gap until it absorbs blue light rather than ultraviolet; do the same calculation non-relativistically and gold comes out silver-coloured, like the metal directly above it. The filled 5d¹⁰ 6s¹ shell is also why it does not corrode, which is why gold artefacts come out of tombs looking new and why gold has been money for five thousand years. It is the most malleable metal known: one gram can be beaten into a sheet a square metre in area, and gold leaf that thin transmits green light. Total human production, everything ever mined, would form a cube about 22 m on a side.

Use 196.97 g/mol in these solvers

Moles from Mass (n = m/M)

n = \frac{m}{M}

Opens with M = 196.97 g/mol already filled in

Gas Density from Molar Mass

\rho = \frac{PM}{RT}

Opens with M = 196.97 g/mol already filled in

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

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

Opens with M = 196.97 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 = 196.97 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 = 196.97 g/mol already filled in

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