Use coulomb's law to calculate the ionization energy in kj/mol of an atom composed of a proton and an electron separated by 185.00 pm.

Coulomb's law mathematically is:

F = kQ₁Q₂/r²

we integrate this with respect to distance to obtain the expression for energy:

E = kQ₁Q₂/r; where k is the Coulomb's constant = 9 x 10⁹; Q are the charges, r is the seperation

Charge on proton = charge on electron = 1.6 x 10⁻¹⁹ C

E = (9 x 10⁹ x 1.6 x 10⁻¹⁹ x 1.6 x 10⁻¹⁹) / (185 x 10⁻¹²)

E = 1.24 x 10⁻¹⁸ Joules per proton/electron pair

Number of pairs in one mole = 6.02 x 10²³

Energy = 6.02 x 10²³ x 1.24 x 10⁻¹⁸

= 746.5 kJ