Question

question 1 - 10
the correct formula for nickel(ii) oxide is
nio
nio₂
ni₂o
ni₃o₂

Explanation:

Step1: Determine the charge of nickel and oxygen

Nickel(III) has a charge of \(+3\) (\(Ni^{3+}\)), and oxygen in oxide has a charge of \(-2\) (\(O^{2 -}\)).

Step2: Use the criss - cross method

To form a neutral compound, we use the criss - cross method. The absolute value of the charge of nickel becomes the subscript of oxygen, and the absolute value of the charge of oxygen becomes the subscript of nickel. So we get \(Ni_2O_3\). But let's check each option:

• For \(NiO\): \(Ni^{2+}\) (nickel(II)) and \(O^{2 -}\), so this is nickel(II) oxide.
• For \(NiO_2\): If \(Ni\) is \(+4\) (nickel(IV)) and \(O\) is \(-2\), this is nickel(IV) oxide.
• For \(Ni_2O\): \(2\times(+2)\) (if we assume \(Ni\) as \(+2\)) and \(O^{2 -}\), not balanced.
• For \(Ni_3O_2\): \(3\times(+2)\) (if \(Ni\) is \(+2\)) and \(2\times(- 2)\), not balanced.

Wait, there is a mistake above. Let's re - do it.
The formula for an ionic compound is \(M_xA_y\) where \(x\times\) charge of \(M=y\times\) charge of \(A\).
Let the charge of \(Ni\) be \(+3\) (\(M = Ni\), charge \(=+3\)) and charge of \(O\) be \(-2\) (\(A = O\)).
We need \(x\times(+3)+y\times(-2)=0\). The smallest non - zero integers \(x = 2\) and \(y = 3\) (since \(2\times3=3\times2\)). So the formula is \(Ni_2O_3\). But if we assume the options have a typo and we consider the valency concept in a simple way (maybe a basic level question):
The compound is made of \(Ni^{3+}\) and \(O^{2 -}\).
We know that in a compound, the sum of positive and negative charges must be zero. Let the formula be \(Ni_xO_y\). Then \(3x-2y = 0\). The ratio \(x:y=2:3\).

Answer:

None of the options \(A.NiO\), \(B.NiO_2\), \(C.Ni_2O\), \(D.Ni_3O_2\) is correct. But if we assume a misprint and consider the valency in a very basic (incorrect from a strict ionic charge balance but maybe in a simple valency - based naming at an elementary level where they just pair the numbers):
If we consider the "old - fashioned" valency (not the correct ionic charge balance in all cases), for \(Ni\) with a "valency" of \(2\) (similar to \(NiO\) which is actually nickel(II) oxide) is wrong for nickel(III). If we force to match the options:
Let's use the formula \(M_aX_b\) where \(a\times\) charge of \(M=b\times\) charge of \(X\).
If \(M = Ni^{3+}\), \(X = O^{2 -}\)
\(a\times3=b\times2\), \(a = 2\), \(b = 3\). But if we consider the options again, maybe there is a mistake in the problem. If we assume that the question means nickel(II) oxide (a common compound), then \(A.NiO\) (where \(Ni^{2+}\) and \(O^{2 -}\)) is the formula for nickel(II) oxide.