Coordination and Oxidation Number in [Co(NH3)5Br]SO4

Coordination Number:
- The coordination number of a complex is the total number of bonds from ligands to the central metal ion.
- In [Co(NH3)5Br]SO4, there are 5 ammonia ligands and 1 bromide ion bonded to the central cobalt ion.
- Therefore, the coordination number of cobalt in this complex is 6.

Oxidation Number:
- The oxidation number of a metal ion is the charge it would have if all the ligands were removed along with the electron pairs that were shared in the bonds.
- In [Co(NH3)5Br]SO4, the sulfate ion (SO4) has a charge of -2.
- The total charge on the complex is 0 (since there is no overall charge mentioned).
- Therefore, the oxidation number of cobalt can be calculated as follows:
- Let x be the oxidation number of cobalt.
- The sum of oxidation numbers of all ligands (NH3 and Br) and the sulfate ion must equal the overall charge of the complex.
- Oxidation number of NH3 (neutral ligand) is 0, Br (halide ion) is -1, and SO4 is -2.
- Hence, x + 0*5 + (-1) + (-2) = 0
- x - 3 = 0
- x = +3 (magnitude only)
Therefore, the coordination number of cobalt in [Co(NH3)5Br]SO4 is 6, and the oxidation number (magnitude only) on the metal ion is +3.