Range profiles of (1-20)-keV Li, B, N, O, F, Na, Mg, and A1 in amorphous Si have been measured by low-energy (\ensuremath{\le}3 keV) secondary-ion mass spectrometry. Mean projected ranges and standard deviations of these ranges were calculated from the as-measured profiles. In order to correct for bombardment-induced profile distortions, effective broadening parameters were extracted from the experimental data. The broadening parameters turned out to be element specific, varying between about 1 nm or less for Li, B, Na, and A1 and up to \ensuremath{\sim} 12 nm for Mg. Corrected mean ranges and standard deviations are compared with tabulated data based upon Lindhard-Scharff-Schi\o{}tt theory. At 10 keV, i.e., the lowest energy covered by tabulations, the experimental and theoretical ranges show very good agreement except for Na and Mg, in which case the measured ranges are 15-20% smaller than predicted. This discrepancy between experiment and theory is attributed to deviations of the projectile-target interaction potential from the assumed universal Thomas-Fermi potential. Range tabulations involving an empirical electronic stopping power, derived by a rigorous scaling and extrapolation of channeling measurements, are shown to be strongly in error in many cases.