  Proton radioactivity has been investigated using the effective liquid drop
model with varying mass asymmetry shape and effective inertial coefficient. An
effective nuclear radius constant formula replaces the old empirical one in the
calculations. The theoretical half-lives are in good agreement with the
available experimental data. All the deviations between the calculated
logarithmic half-lives and the experimental values are less than 0.8. The
root-mean-square deviation is 0.523. Predictions for the half-lives of proton
radioactivity are made for elements across the periodic table. From the
theoretical results, there are 11 candidate nuclei for proton radioactivity in
the region $Z <51$. In the region $Z >83$, no nuclei are suggested as probable
candidate nuclei for proton radioactivity within the selected range of
half-lives studied.
