Polyatomic ions and their charge

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Discussion Overview

The discussion revolves around the determination of the charge of polyatomic ions, specifically focusing on the selenate ion (SeO4) and its charge of -2. Participants explore the reasoning behind the charge assignment and the relationship between oxidation states and net charge.

Discussion Character

  • Exploratory, Technical explanation, Conceptual clarification

Main Points Raised

  • One participant questions the necessity of memorizing the charges of polyatomic ions and seeks to understand how to deduce the charge from the constituent atoms, using selenate as an example.
  • Another participant suggests that the charge can be inferred from the presence of unpaired electrons in the oxygen atoms, indicating a charge of -2.
  • Aldo expresses gratitude for the clarification regarding the bonding in the SeO3 anion and seeks further understanding of the bonding structure and charge assignment in SeO4.
  • There is a request for a simpler explanation regarding how SeO4 acquires a charge of -2, indicating some confusion about the diagrams and concepts presented.

Areas of Agreement / Disagreement

Participants do not appear to reach a consensus on the explanation of how the charge of SeO4 is determined, as there are differing levels of understanding and requests for clarification.

Contextual Notes

Some participants express uncertainty about the diagrams and the reasoning behind charge assignments, indicating that further clarification may be needed regarding the underlying principles of electron pairing and oxidation states.

icefire23
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This question is regarding polyatomic ions and their charge. I have always been told that I have to memorize the charge of polyatomic ions. The question is whether I can determine by myself the charge of two atoms when they join together to form a polyatomic ion. For example Se and O can form selenate SeO4, this polyatomic ion has a charge of -2. I would like to know why is the charge -2? But what I know the sum of all oxidation states of the joining ions must be equal to the net charge of the ion. But what happens then if I do not know the net charge of the ion? Hopefully these questions are not too silly. Thanks before hand, Aldo.
 
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Selenate.png


Because the ion is like this. There is 1 unpaired electrons on 2 oxygen atoms, giving it a charge of 2-.

For these kinds of ions, just try pairing up their electrons to get a stable electron configuration until you only have unpaired electrons left. You can then deduce the charge of the whole ion from that.
 
Ok, seeing the bonds in the ion helped. Thank you very much for your help. So, when I have the SeO3 anion with a charge of -2, I would have 1 Selenium Oxygen double bond and two Selenium Oxygen single bonds, with an electron pair in the Selenium? Aldo.
 
yeap.

btw, what's aldo?
 
Thanks again for your help. Hahahaha..Aldo is just my name : )
 
Bloodthunder said:
Selenate.png


Because the ion is like this. There is 1 unpaired electrons on 2 oxygen atoms, giving it a charge of 2-.

For these kinds of ions, just try pairing up their electrons to get a stable electron configuration until you only have unpaired electrons left. You can then deduce the charge of the whole ion from that.

I still don't get how SeO4 acquires a charge of 2-. I don't understand the diagram above either. Please explain in more plain language.
 

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