group number of an element represents the valency with respect to: (a)hydrogen (b)oxygen (c)carbon (d)helium how?

group number of an element represents the valency with respect to:
(a)hydrogen (b)oxygen
(c)carbon (d)helium


1 Answers

AKASH GOYAL AskiitiansExpert-IITD
420 Points
13 years ago

Dear Pooja

Elements are put into groups according to how many valence electrons they have. You'll recall that the valence electrons are the electrons in the outer most shell of an atom. It is the number of valence electrons that generally determine the chemistry of atoms, and that's what the periodic table is all about.
A quick way to determine the number of valence electrons for a representative element is to look at which group is it in. Elements in group Ia have 1 valence electron which is equal to the valence electron of Hydrogen. Elements in group IIa have 2 valence electrons. Can you guess how many valence electrons elements in group VIa have? If you guessed 6 valence electrons, then you are correct! The only group of representative elements that this method doesn't work for is group 0. Those elements certainly have more than 0 valence electrons; in fact, all of them except for helium have 8 valence electrons. Why doesn't helium have 8 valence electrons? Think for a moment about how many electrons helium has - it has a total of only two electrons, so helium only has 2 valence electrons.
So generally speaking, the number of valence electrons stays the same as you go up or down a group

All the best.                                                           


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