The hybridization and magnetic behaviour of cobalt ion in [Co(NH$$_3$$)$$_6$$]$$^{3+}$$ complex, respectively is

For the complex Hexaamminecobalt(III) complex:

• Oxidation state of cobalt $$= +3$$
• Electronic configuration of $$Co^{+3} = 3d^{6}$$
  

Since $$NH_3$$​ acts as a strong field ligand with $$Co^{+3}$$ , the $$3d$$ electrons pair up in the lower energy orbitals.

So the arrangement becomes:

• $$t^6_{2g}$$ $$e^0_g$$
• No unpaired electrons

Therefore:

• Hybridisation = $$d^{2}sp^{3}$$ (inner orbital octahedral complex)
• Magnetic behaviour = Diamagnetic

So the final answer is:

$$d^{2}sp^{3}$$ hybridisation and diamagnetic nature.