Which atom would carry the formal charge

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Xinye_Jiang_1A
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Which atom would carry the formal charge

Postby Xinye_Jiang_1A » Sun Jul 23, 2017 8:59 pm

TA told me the atom that has the highest electronegativity in the anion would carry the negative charge, like the oxygen in IO3- carries the -1 charge. Whys that? How can we determine which atom has the highest electronegativity? Will the info be given?

Chem_Mod
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Re: Which atom would carry the formal charge

Postby Chem_Mod » Sun Jul 23, 2017 10:43 pm

Electronegativity values typically won't be given, but using your knowledge of electronegativity trends in the periodic table, you should be able to reason out which of 2 atoms is more electronegative.

A negative formal charge means the atom that's carrying it is pulling more of the electron density toward itself. By the definition of electronegativity, it should make sense that the more electronegative atom should carry the negative formal charge (if possible).

mayapartha_1D
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Re: Which atom would carry the formal charge

Postby mayapartha_1D » Sun Oct 22, 2017 4:48 pm

Hello!

The most electronegative atom would hold the electron as, by the definition of electronegativity, the atom holds a higher affinity for taking electrons.

Hope this makes sense, and good luck.

Clarisse Wikstrom 1H
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Re: Which atom would carry the formal charge

Postby Clarisse Wikstrom 1H » Fri Oct 27, 2017 11:02 pm

If you haven't memorized the periodic trends already, it's also important to know HOW they exists if you are not given the electronegativities. EN increases as you go to the right of the periodic table because as more valence e- are added, they become closer to an octet. You can think of EN as how much an atom wants to gain an e- to obtain an octet. For example, flourine has higher EN than oxygen because it only needs one e- to obtain an octet, whereas oxygen needs two. EN is like greediness, the flourine is more greedy to get the e-. EN also increases as you go up the periodic table because since the atom is smaller, the nucleus will have a stronger pull on the outer electrons because less electrons are in its way.
Of course, there are exceptions to these trends, but as long as you know how the trends work, you'll be able to figure out most problems.


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