Electrolysis Calculator
One amp for one hour plates 1.19 g of copper — electrolysis is bookkeeping in electrons and nothing else.
The formula
mass = I t M / (n F) ; F = 96485 C per mole of electrons
Charge is the currency
Faraday's insight was that electrolysis is bookkeeping in electrons. Current times time is charge, charge divided by the Faraday constant is moles of electrons, and the stoichiometry of the half-reaction converts those into moles of product. Nothing else enters.
Why the charge on the ion matters so much
Depositing a mole of copper from Cu²⁺ takes two moles of electrons; a mole of aluminium from Al³⁺ takes three. Aluminium is also light, so the mass per coulomb is small twice over. That is the reason aluminium smelting is one of the most electricity-hungry industrial processes there is, and why smelters are built next to hydroelectric dams.
Models, and where they stop
Slater's rules, the Kapustinskii equation and Pauling's ionic-character expression are all empirical fits, not derivations. They were built to reproduce measured numbers with arithmetic simple enough to do by hand, and they succeed at that within perhaps five or ten per cent. Where a page here quotes one, it says which — a figure from a fitted rule and a figure from a Born-Haber cycle are not the same kind of thing, even when they agree.