2.What value is the closest estimate of Zeff for a valence electron of the calcium atom? (A) 20 (B) 40 (C) 2 (D) 6 (E) 1

12.The spectrochemical series is I – < Br– < Cl– < F– < OH– < H2O < NH3 < en < NO2 – < CN– Which of the following complexes will absorb visible radiation of the highest energy (shortest wavelength)? (A)[Co(OH)6] 3– (B)[Co(NH3)6] 3+ (C)[Co(I)6] 3– (D)[Co(H2O)6] 3+ (E)[Co(en)3] 3+