We present a new approach to planetary system architecture in which orbital configurations emerge from a balance between gravitational and Lorentz forces. Using a 1/√r scaling law derived from plasma physics, we define a theoretical maximum mass for planets at each orbital radius, calibrated against the most massive planet in any system — Jupiter in the Solar System. Applying the same scaling to orbital velocities reproduces the results of Kepler’s and Newton’s laws without explicitly invoking them, introducing a new empirically derived constant that characterises planetary motion.Extending this framework to planetary spacing reveals harmonic patterns across systems. For instance, Saturn’s moons follow a Fibonacci sequence related to the golden ratio, while the Kepleru201190 system exhibits orbital spacing consistent with simple prime-fraction harmonics. These patterns suggest that orbital mass limits, velocities and spacing may be governed by a universal electromagnetic—gravitational principle. This model provides a predictive framework for planetary system structure and offers testable hypotheses for both Solar System and exoplanetary architectures.