We use an AT‐cut quartz resonator with metal electrodes as the substrate. The material properties of the quartz are well characterized, and the resonant frequency can be determined accurately (1 part in 108or better). When a particle was placed on the electrode, the resonant frequency increased, contrary to mass loading theory. If the particle‐resonator system is modeled mechanically as a coupled oscillator system, indeed the resonant frequency should increase. The increase is determined by the bonding force constant between particle and substrate, which we calculate. Experimental data on the autohesion force constants of Au spheres on etched Au electrodes in air is presented.