In case of [Ni(NH3)6]Cl2 complex, the oxidation state of nickel atom is +2 .The atomic number of nickel atom, 28 and that of Ni(II)ion is 26 .
Valence shell electronic configuration of Ni(II) ion is [ Ar ] d8 . Coordination number of central metal Ni(II)ion : 6 . Arrangement of [Ni(NH3)6]Cl2 complex is Octahedral.
Now, the paramagnetic character of above said octahedral Ni(II) complex does not explained on the basis of crystal field theory.
Because, the ligand NH3 is a strong field ligand. So, under the influence of the octahedral crystal field, the five degenerate d-orbitals of Ni(II) ion are splitted into two sets of energetically different orbitals.