= Solution
A classically accelerating Coulomb <electron> radiates and loses <orbital energy>, so a stable nonradiating <orbit (dynamical system)>[orbit] is impossible within that unmodified theory. Bohr instead postulates stationary nonradiating <orbit (dynamical system)>[orbits], quantized <angular momentum> $\mu vr=n\hbar$ and <photon emission>/absorption with $h\nu=E_i-E_f$. Here $\mu=m_eM/(m_e+M)$ describes <relative motion>. The angular-momentum condition is the standing-wave relation $\boxed{2\pi r=n\lambda_{\mathrm{dB}}}$ for the relative <orbit (dynamical system)>[orbit]. These are additional quantum postulates, not consequences of classical radiation theory.
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