Is there any relationship between the valency of an element and the number of electrons its atom has in its outermost shell? Predict the valencies of helium (He), phosphorus (P), sulphur (S) and neon (Ne). The atomic numbers of these elements are, 2, 15, 16 and 10, respectively.
Answers
Is there any relationship between the valency of an element and the number of electrons its atom has in its outermost shell?
Before knowing the relation let's take a quick peek into their definitions
Valency
It is the combining capacity of an element with the atoms of another element to form a chemical compound.
And who combines?
They are the electrons.
Valence Electrons
These are the electrons that combine with other atoms to form a chemical compound.These electrons are the ones that are present in outermost shell of an element , and they only take part in forming new compounds not all the electrons.
So, the valency of an element is the number of valence electrons lost,gained or shared when forming a compound.An atom loses,gains or shares electrons so as to achieve the noble gas configuration.
For, example Na (sodium) , Cl (Chlorine)
Na has the electronic configuration --> 2,8,1
It has once valence electron, so this 1 electron takes part in reactions,hence this the valency of Na (+1).
Cl has the electronic configuration --> 2,8,7
It has 7 valence electrons, but it can't lose so many because it would involve a lot of energy, so it gains an electron.So, its valency is - 1.
Predict the valencies of helium (He), phosphorus (P), sulphur (S) and neon (Ne). The atomic numbers of these elements are, 2, 15, 16 and 10, respectively.
helium = 0
phosphorus = 3
sulphur = 2
neon = 0
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