The 1 st , 2 nd and the 3 rd ionization enthalpies, I 1 , I 2 and I 3 , of four atoms with atomic numbers n , n + 1 , n + 2 , and n + 3 , where n < 10 , are tabulated below. What is the value of n ? Atomic number Ionization Enthalpy (kJ/mol) I 1 I 2 I 3 n 1681 3374 6050 n + 1 2081 3952 6122 n + 2 496 4562 6910 n + 3 738 1451 7733