  The alpha decay half-lives of recently synthesized superheavy nuclei (SHN)
are calculated by applying a new approach which estimates them with the help of
their neighbors based on some simple formulas. The estimated half-life values
are in very good agreement with the experimental ones, indicating the
reliability of the experimental observations and measurements to a large extent
as well as the predictive power of our approach. The second part of this work
is to test the applicability of the Wentzel-Kramers-Brillouin (WKB)
approximation for the quantum mechanical tunneling probability. We calculated
the accurate barrier penetrability for alpha decay along with proton and
cluster radioactivity by numerically solving Schr\"odinger equation. The
calculated results are compared with those of the WKB method to find that WKB
approximation works well for the three physically analogical decay modes.
