The formula of nickel oxide is Ni0.98O1.00.
Therefore, the ratio of the number of Ni atoms to the number of O atoms,
Ni : O = 0.98 : 1.00 = 98 : 100
Now, total charge on 100 O2− ions = 100 × (−2) = −200
Let the number of Ni2+ ions be x.
So, the number of Ni3+ ions is 98 − x.
Now, total charge on Ni2+ ions = x(+2) = +2x
And, total charge on Ni3+ ions = (98 − x)(+3) = 294 − 3x
Since, the compound is neutral, we can write:
2x + (294 − 3x) + (−200) = 0
⇒ −x + 94 = 0
⇒ x = 94
Therefore, number of Ni2+ ions = 94
And, number of Ni3+ ions = 98 − 94 = 4
Hence, fraction of nickel that exists as Ni2+
And, fraction of nickel that exists as Ni3+
Alternatively, fraction of nickel that exists as Ni3+ = 1 − 0.959 = 0.041
