Which of the following statements is/are wrong?
a. van der Waals' radius of iodine is more than its covalent radius
b. All isoelectronic ions belong to same period of the periodic table
c. I.E.1 of N is higher than that of O while I.E.2 of O is higher than that of N
d. The electron affinity N is almost zero while that of P is 74.3 kJ mol−1