Question

what is valency?Give example of any two elements showing variable valency with their names​

Answer 1

Explanation:

Some elements differ in their capacity to combine with other elements depending on the nature of the reaction; this property is called variable valency. For example, the iron in ferrous oxide exhibits a valency of +2, whereas in ferric oxide, it has a valency of +3.

Answer 2

Valency is the number of electrons needed to be added or removed from the outermost shell of the atom so that it could get a completely filled outermost shell or in other words valance shell.

Let us take an example of Sodium(Na):-
2, 8, 1.
Here the outermost shell is only having one electron. It can either loose 1 electron and make it 2,8 which is a completely filled unit or it can even gain 7 electrons which would make it 2,8,8 which is also a completely filled unit.

In this case losing 1 electron instead of gaining of 7 electrons would be the most practical thing, therefore sodium attains its valency by loosing 1 electron.

Therefore the *Valancy of Sodium is 1*.



Now let us take the example of Chlorine(Cl), 2,8,7. Here there are two possibilities. It can either loose 7 electrons to make it 2,8 or gain 1 electron which would make t 2,8,8. Both are a completely filled unit.

Here gaining 1 electron would be easier than loosing 7 electrons to get a completely filled outermost shell.

So, 1 electron must be gained to get a completely filled outermost shell.

Therefore the valency of Chlorine is 1.

Always remember that valency is the shortest number of electrons which is gained or lost to get a completely filled valance shell or outermost shell.


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