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Covalent Character

Posted: Fri May 18, 2018 3:59 pm
by Fiona Grant 1I
In class, we talked a bunch about how ionic bonds have covalent character. What exactly does it mean for a bond to have "covalent character"? There was something about "highly distorted electrons" and "highly polarizable" but I'm having some trouble understanding this.

Re: Covalent Character

Posted: Fri May 18, 2018 3:59 pm
by Natalie Noble 1G
Ionic bonds have unequal sharing of electrons, while covalent bonds have equal sharing of electrons. Ionic bonds are a bond between oppositely charged ions, so the electrons are not equally shared, the metal loses electrons to become positively charged (cation), and the nonmetal accepts the electrons to become negatively charged (anion).
However, since the cation is positively charged, it will attract the electrons surrounding the anion. And the pulled in ions cause distortion (a distorted electron cloud).
Since the cation is pulling in electrons from the anion, the electrons are being shared more evenly, hence making it have covalent character.
The degree of this covalent character is dictated by the cation’s polarizing power (ability to pull electrons in) and the anion’s polarizability. These factors together cause the distortion and when the electrons are highly distorted they are highly polarizable.

Re: Covalent Character

Posted: Fri May 18, 2018 4:00 pm
by Fiona Grant 1I
Ok, that clears it up, thank you!

Just a follow-up question: what is the general trend for increasing covalent character of an ionic bond? (In other words, what in the bond changes in order for covalent character to increase?)

Re: Covalent Character

Posted: Fri May 18, 2018 4:02 pm
by Natalie Noble 1G
cation’s polarizing power:
Increase in charge and small cation = more charge density (polarizing power)

anion’s polarizability:
larger the anion = easier it is to distort