In the compound [Co NH3 6]Br3, the central metal atom is cobalt Co . To determine its oxidation state, we need to consider the charges of the ligands and counterions.NH3 is a neutral ligand, meaning it does not contribute any charge to the complex. The complex has a charge of +3 due to the three bromide ions Br- acting as counterions. Since there are no other charges within the complex, the oxidation state of cobalt must be +3 to balance the overall charge.So, the oxidation state of the central metal atom cobalt in the compound [Co NH3 6]Br3 is +3.