What is the electrostatic potential energy (in joules) between an electron and a proton that are separated by 54 pm?

The formula for calculating the electrostatic potential is given as:

U = (1/4πε0) (qp * qe/r)

where the variables are:

ε0 = permittivity of space = 8.854187817620 * 10^-12 A^2⋅s^4⋅kg-1⋅m-3

qp = charge of proton = 1.60217662 * 10-19 coulombs

qe = charge of electron = - 1.60217662 * 10-19 coulombs

r = distance between the two = 54 pm = 5.4 * 10-11 m

So calculating for potential energy U:

U = (1 / (4π*8.854187817620)) (1.60217662 * 10-19 * - 1.60217662 * 10-19 / 5.4 * 10-11)

U = 5.33 x 10^-11 J