Electron speed in nth Bohr orbit (hydrogenic) (v_n = Zαc/n)

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v_n = Zαc/n

What each symbol means

SymbolWhat it stands for
cSpeed of light in vacuum
v_nOrbital speed in nth orbit
\alphaFine-structure constant ≈ 1/137

When to use this

Bohr model hydrogenic atom; non-relativistic estimate (v ≪ c still checked per n,Z).