The formula for electrostatic potential is:
U = (1/4piε0)·(qpqe/r)
- ε0= permittivity of free space = 8.854187817620 × 10−12 A2⋅s4⋅kg−1⋅m−3
- qp = proton charge = 1.60217662 × 10-19 coulombs
- qe = electron charge = -1.60217662 × 10-19 coulombs
- r = separation distance = 50 pm = 5 × 10−11 m
Note that I've put all units into standard SI units so the answer is in joules. Plug the values in and compute the answer. You may want to round some of the numbers to 4 or 5 significant units then round your answer as needed.