How are #"valence"# and #"valency"# defined?

1 Answer
Mar 16, 2017

Answer:

Traditionally, valence was the number of hydrogens (hydrides or protons) that combined with the element. It is a bit of an old-fashioned term.

Explanation:

And thus carbon has a valency of #4# in methane, nitrogen has a valence of #3# in ammonia..........

Now valency is a fluid concept, and it is usually better to use oxidation states and number, which is another concept you have to absorb. See here for a start. With metal ions, i.e. #M^(n+)#, when we speak of the univalent, #n=1#, bivalent, #n=2#, tervalent, #n=3#, ions, we refer to the #M^(+)#, #M^(2+)#, and #M^(3+)# ions. And, here, clearly, valence reflects oxidation state.

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