Energy loss and straggling of heavy ions have been studied. The conventional target excitation contributions are estimated on the basis of the dielectric function method together with the local electron density model. In addition, electron capture contributions are estimated in a classical atomic picture, which are expressed by simple analytical forms. The average charge of traversing ions is determined by an empirical formula. Electron capture contributions becomes large and comparable at relatively low velocities, where they are proportional to the average charge of ions. At high velocities, on the other hand, these contributions are negligible. Charge exchange processes are found to contribute to the slowing-down as corrections.