Assume the valence electron in a sodium atom is on average 0.19nm from the nucleus, while that in a potassium atom is on average 0.28nm away. If each valence electron experiences an effective nuclear charge of +1.0, which of the following is the best estimate of the ratio IEKIENa of their first ionization energies?
a) 0.68
b) 1.5
c) 2.2
d) 0.56