F = GmM/R^2 = ma => GM/R^2 = a
G= 6.67x10^-11
M proton = 1.67x10^-27
m Electron = 9.11 x10^-31
R = 0.053 x 10^-9
a = -2.10167…x10^-27
a = -2.1017x10^-27
Treat "a" as gravity, because the electron is like free falling on the proton, that’s why it is expressed as negative.
Change in Distance = vi(t) + at
-0.053x10^-19 = 0 + -2.1017x10^-27 (t)
t = 521768.092 secs or 520000 secs <== sig fig