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9C.5 7th Edition

Posted: Mon Dec 03, 2018 9:30 pm
by Tessa Lawler 1A
I was wondering if someone could explain this question to me.
It says: "Which of the following ligands can be polydentate?"
a) HN(CH2CH2NH2)2 b)C03 2- c)H20 d)oxalate
For the answers, the book says:
a) Has 3 N atoms w/ a lone pair, so can be tridentate
b) can bind to a metal ion through either one or two Oxygen atoms - therefore, it is mono- or bidentate
c) H20 is always monodentate
d) The oxalate ion can bond through 2 oxygen atoms and is usually bidentate
Here's my question(s): Are we supposed to have rules for common ligands memorized? How are we supposed to know these rules? Is there something we can do to determine if a ligand can be polydentate if we're not sure/if we don't recognize the specific ligand?

Re: 9C.5 7th Edition

Posted: Tue Dec 04, 2018 12:44 pm
by AustinGrove3B
You would have to count the amount of electronegative atoms with lone pairs. The lone pair would form coordinate bonds with the metal. For the first question, there are 3 N in the equation, so it will form three bonds. H20 has one O, so it will form one bond. CO3 has two Os with lone pairs, so it can either form 1 or 2 bonds.

Re: 9C.5 7th Edition

Posted: Tue Dec 04, 2018 7:31 pm
by Lia Inadomi 1I
If you are unfamiliar with a ligand you can draw a Lewis structure to help you determine the number of lone pairs