Question

Analysis shows that nickel oxide consists of nickel ion with 96% ions having $d^{8}$ configuration and 4% having $d^{7}$ configuration. Which amongst the following best represents the formula of the oxide?

• A. $Ni_{1.02}O_{1.00}$
• B. $Ni_{0.96}O_{1.00}$
• C. $Ni_{0.98}O_{0.98}$
• D. $Ni_{0.98}O_{1.00}$

Answer 1

Answer: (D)

$Ni=3d^{8}4s^{2}$ (Atomic number = 28)
So $Ni^{2 +}=3d^{8}$ and $Ni^{3 +}=3d^{7}$
Hence, 96% ion of $Ni^{2 +}$ and 4% ions of $Ni^{3 +}$ are present.
Let number of $O^{2 -}$ ion present in the crystal = x
Using electroneutrality rule,
Total positive charge = Total negative charge
$96\times 2\left(\right.+vecharge\left.\right)+4\times 3\left(\right.+vecharge\left.\right)$
$=x\times 2\left(\right.-vecharge\left.\right)$
So $96\times 2+4\times 3-2x=0$
So x = 1.02
Hence formula of the crystal is $Ni_{1.00}O_{1.02}$ or $Ni_{0.98}O_{1.00}$ .