Question

Assertion: Nickel is a metal and it conducts electricity through its valence shell electrons.
Reason: Nickel sulphate solution conducts electricity through its ions.
A) Both Assertion and Reason are true and Reason is the correct explanation of Assertion.
B) Both Assertion and Reason are true but Reason is not the correct explanation of Assertion.
C) Assertion is true but Reason is false
D) Assertion is false but Reason is true
E) Both Assertion and Reason are false.

Answer 1

We know that metals are good conductor of electricity due to loosely bound valence electrons and nickel has two unpaired electrons in its $d$ orbital of the penultimate shell. We also know that nickel mostly occurs in the $+ 2$ oxidation state when dissociated in water.

Complete step by step answer:
We know that the atomic number of nickel is 28.
Let us try to write the electronic configuration of nickel:
${\text{N}}{{\text{i}}_{{\text{28}}}}{\text{ = 1}}{{\text{s}}^{\text{2}}}{\text{2}}{{\text{s}}^{\text{2}}}{\text{2}}{{\text{p}}^{\text{6}}}{\text{3}}{{\text{s}}^{\text{2}}}{\text{3}}{{\text{p}}^{\text{6}}}{\text{3}}{{\text{d}}^{\text{8}}}{\text{4}}{{\text{s}}^{\text{2}}}$
From the electronic configuration of nickel, it is clear that the $3d$ orbital of nickel is not completely filled and it has two unpaired electrons.
We know that to attain a stable configuration nickel can donate the two unpaired electrons. As the donation of electrons takes place we can say that nickel is a metal.
So, Nickel can conduct electricity because the valence electrons are loosely bound.
Here, valence electrons are the two unpaired electrons of $3d$ orbitals.
So, the valence electrons are free to move across the material.
Hence, we can say that nickel is a metal and it can conduct electricity through its valence electrons.
The assertion is true.
Now let us focus on the reason statement:
We know that nickel sulphate when dissolved in water undergoes dissociation.
We can show the dissociation of nickel sulphate as follows:
$NiS{O_4} \to N{i^{ + 2}} + S{O_4}^{ - 2}$
As we can see that the dissociation leads to the formation of ions and these ions are responsible for the conduction of electricity by nickel sulphate solution.
Hence we can say that nickel sulphate solutions conduct electricity through its ions.
The reason is also true.
But the nickel sulphate solution conducting electricity does not justify that the nickel is a metal and it conducts electricity through its valence electrons.

Therefore, we can conclude that the correct answer to this question is option B.

Note: Mostly in general, all metals conduct electricity due to free electrons in solid. In liquid, it conducts electricity through ions. In this type of question we must always focus if the statement provided under reason is able to justify the statement provided under assertion. Here we can get confused between options A and option B.