CBSE Class 9 Answered

Dear Student

 

The valency of an element is the measure of electrons it needs or needs to loose to obtain a stable structure (a noble gas structure, such as helium, neon, argon ...) for example in NaCl, sodium has 11 electrons which means 1 valence electron, chlorine has 17 electrons which means it has -1 valence electrons; so sodium looses 1 electron and chlorine gains that electron so sodium ends up with 10 electrons (Neon's electron structure) and chlorine ends up with 18 electrons (Argon's electron structure) the number of outer electrons. Noble elements are the most stable elements (thats why they don't react well and stay alone, like helium) so all the other elements try to obtain the noble electron structure. Elements usually gain or loose 4 electrons.

 

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