Alpha particle touching Gold nucleus

[kraigandrews]

Homework Statement

If the radius of the gold nucleus is 6.47 fm, and the radius of the α particle is 2.36 fm, then what is the minimum required kinetic energy for the α particle if we want the two nuclear surfaces to touch in a head-on collision?

Homework Equations

U_e=(kq¹q²)/r

The Attempt at a Solution

so using U_e=KE
q₁=2
q₂=79

then it should be straightforward plug and chug, however the KE this yields is very high, around 3E45 eV this cannot be right, what am I doing wrong?

 

[NascentOxygen]

The alpha-particle moves from infinity to a distance of r_alpha + r_au femtometres from the centre of the gold nucleus.

 

[ehild]

The Attempt at a Solution

so using U_e=KE
q₁=2
q₂=79

what is the unit of q?

ehild