1. What is the total charge of the neptunium nucleus? $($The neutral neptunium atom has $93$ electrons.$)1\mathrm{.}49\times 10^-$¹⁷m

2. What is the magnitude of its electric field at a distance of $4\mathrm{.}18\times 10^-$¹⁰m from the nucleus?

3. What is the magnitude of the force on an electron at that distance?

4. What would the magnitude of the force be if the distance of the electron from the nucleus were halved?