How can the valency of an element be determined if its electronic configuration is known?

The electronic configuration of elements (particularly the elements belonging to group 1, 2 and 13-18) can help in determining the valency of the element. For metals, which have a tendency to lose electrons, the valency is equal to the number of electrons present in the valence shell. This is because the element requires to lose these many electrons to achieve a noble gas configuration. For example the electronic configuration of sodium is 2, 8, 1. It needs to lose one electron to achieve the noble gas configuration. Hence its valency is 1.

Similarly, for non-metals, the valency is equal to the number of electrons required to gain in order to complete their octet and achieve a noble gas configuration. For example, the electronic configuration of chlorine is 2, 8, 7. It needs to gain one electron to complete its octet. So, it valency is 1. 

In brief, we can say that for elements which contain less than 4 electrons in their valence shell, the valency is equal to the number of valence electrons. On the other hand, the elements which contain more than 4 electrons in their valence shell, the valency is equal to (8 - number of valence electrons). For elements containing 4 electrons in the valence shell, the valency is 4. 

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 We can determine the valency by checking how much more electrons is needed by the element to reach its octate state 

For eg An element Oxygen whose outermost shell has 6 electrons need two electrons to reach its octate so its valency is -2.

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There is nothing called -2 valency.....for your information aakash.messi...  ...... 

 

Coming to the question if the valence electrons are 1, 2 , 3.....then the valency is the no of the valence electrons  ...here...i.e. 1,2,3.................these are electropositive elements as they give out electrons.....

 

now for electronegative elements ...ie...elements having valence electrons 5,6,7 ...then  the valency can be found out by subtracting it from 8....for eg valency of element having valence electrons== (8-5)=3.......

and the valencey of noble elements is 0 as 8-8(no of valence electron of noble gases)....

now we come to valence electron 4 .....they show co valency as they dont want to give or take electrons......anyways the valency will be 4.......

 

 

hope u got ur answer........have a great day....

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