Ionic character  [ENDORSED]

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Artin Allahverdian 2H
Posts: 76
Joined: Fri Sep 28, 2018 12:26 am

Ionic character

Postby Artin Allahverdian 2H » Sat Nov 03, 2018 9:18 pm

Why is CF4 more ionic than CH4? To me it seems that the electronegativity difference is more between C and H than between C and F just because H is farther from C than F is. Is there something else that I didn’t put into account?

Maya_Peterson1C
Posts: 62
Joined: Fri Sep 28, 2018 12:28 am

Re: Ionic character

Postby Maya_Peterson1C » Sat Nov 03, 2018 9:22 pm

If you look up the electronegativity values of H, C, and F, they are 2.1, 2.5, and 4.0 respectively. So, the electronegativity values for Carbon and Hydrogen are a lot closer than the value for Fluorine. Just because they appear closer on the periodic table doesn't necessarily mean their values are closer.

mahika_nayak_3L
Posts: 60
Joined: Fri Sep 28, 2018 12:26 am

Re: Ionic character  [ENDORSED]

Postby mahika_nayak_3L » Sat Nov 03, 2018 9:27 pm

Fluorine is much more electronegative than Hydrogen is because Fluorine has a greater electron affinity (increases from left to right and down to up) and a higher ionization energy (energy needed to remove the most loosely attached electron). Because the electronegativity of Fluorine is greater compared to Hydrogen, there is also a greater difference between this electronegativity value and that of Carbon. Basically, the Fluorine atoms have a stronger hold on the shared electrons as compared to the hold that Hydrogen has, so the covalent bonds of CF4 exhibit more ionic character.

Bingcui Guo
Posts: 30
Joined: Fri Sep 28, 2018 12:19 am

Re: Ionic character

Postby Bingcui Guo » Sun Nov 04, 2018 8:34 am

You can see by calculating the difference of electronic affinity. C-F is larger than C-H

Christopher Wendland 4F
Posts: 30
Joined: Fri Sep 28, 2018 12:29 am

Re: Ionic character

Postby Christopher Wendland 4F » Sun Nov 04, 2018 9:12 am

F is way more electronegative than C and H is only a bit less electronegative than C so the difference is greater between C and F

Artin Allahverdian 2H
Posts: 76
Joined: Fri Sep 28, 2018 12:26 am

Re: Ionic character

Postby Artin Allahverdian 2H » Mon Nov 05, 2018 6:56 am

I think for a question like this he would have to give you the electronegativity values just because it is hard to decipher the electronegativity comparisons just by looking at the periodic trends.


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