Discuss and compare the trend in ionization enthalpy of the elements of Group 1 with those of Group 17 elements.
a) Ionization enthalpy decreases down the group in both groups
b) Ionization enthalpy increases down the group in both groups
c) Ionization enthalpy increases down the group in Group 1 and decreases in Group 17
d) Ionization enthalpy decreases down the group in Group 1 and increases in Group 17