The Student Room Group

Covalent character explanation

Hi,

Could someone please explain covalent character to me, specifically why it causes an increase in bond strength? I understand that generally ionic bonds are stronger than covalent, so why does covalent character increase bond strength? Also, how does how polar a covalent bond is affect strength? Thanks.
Reply 1
Original post by Har6547
Could someone please explain covalent character to me, specifically why it causes an increase in bond strength? I understand that generally ionic bonds are stronger than covalent, so why does covalent character increase bond strength? Also, how does how polar a covalent bond is affect strength? Thanks.

covalent bonds involve the sharing of a pair of electrons between 2 atoms, where both atoms have an electrostatic attraction for the shared pair of electrons. The main factor affecting strength of covalent bonds is the electronegativity of each of the covalently bonded atoms. Electronegativity is the ability to pull a shared pair of electrons towards itself (This is dependent on factors such as nuclear charge, shielding & atomic radii). Where 1 atom of the bond has a greater electronegativity, it'll pull the shared pair of electrons towards itself (electrons still remain shared between the 2 but are just now closer to the electronegative atom). This is referred to as a polar bond. The greater the difference in electronegativity, the greater the polarity of the covalent bond, the greater the covalent bond strength
Reply 2
Original post by samiul.tr
covalent bonds involve the sharing of a pair of electrons between 2 atoms, where both atoms have an electrostatic attraction for the shared pair of electrons. The main factor affecting strength of covalent bonds is the electronegativity of each of the covalently bonded atoms. Electronegativity is the ability to pull a shared pair of electrons towards itself (This is dependent on factors such as nuclear charge, shielding & atomic radii). Where 1 atom of the bond has a greater electronegativity, it'll pull the shared pair of electrons towards itself (electrons still remain shared between the 2 but are just now closer to the electronegative atom). This is referred to as a polar bond. The greater the difference in electronegativity, the greater the polarity of the covalent bond, the greater the covalent bond strength


Ok thank you. What about covalent character in ionic bonds, why does that increase bond strength?
Original post by Har6547
Hi,

Could someone please explain covalent character to me, specifically why it causes an increase in bond strength? I understand that generally ionic bonds are stronger than covalent, so why does covalent character increase bond strength? Also, how does how polar a covalent bond is affect strength? Thanks.


Bold part: Covalent character means that the ions within an ionic compound are distorted, causing the ions to end up in a closer proximity to one another in the lattice than would be expected with the perfect ionic model. The fact this brings the ions closer means greater attraction between the ions, so more energy is needed to separate them, indicating greater bond strength.

Italic part: Not true. Covalent bonds tend to be stronger as there is overlap between the participating atoms, meaning the electrostatic attraction between the nuclei and participating electrons is very strong. Try adding water to most covalent compounds under ambient conditions and you can generally expect little to no bond breakage. Try adding water to your typical ionic compound and it should dissolve, indicating that the bonds have been broken (albeit only temporarily).

Underlined part: Polarity leads to partial positive and negative charges, so naturally you get stronger electrostatic attraction. This means a stronger bond overall. The more polar the bond, the stronger (in theory) it should be.
Reply 4
Original post by TypicalNerd
Bold part: Covalent character means that the ions within an ionic compound are distorted, causing the ions to end up in a closer proximity to one another in the lattice than would be expected with the perfect ionic model. The fact this brings the ions closer means greater attraction between the ions, so more energy is needed to separate them, indicating greater bond strength.

Italic part: Not true. Covalent bonds tend to be stronger as there is overlap between the participating atoms, meaning the electrostatic attraction between the nuclei and participating electrons is very strong. Try adding water to most covalent compounds under ambient conditions and you can generally expect little to no bond breakage. Try adding water to your typical ionic compound and it should dissolve, indicating that the bonds have been broken (albeit only temporarily).

Underlined part: Polarity leads to partial positive and negative charges, so naturally you get stronger electrostatic attraction. This means a stronger bond overall. The more polar the bond, the stronger (in theory) it should be.


Ok thank you, this has been very helpful :smile:
Original post by Har6547
Ok thank you, this has been very helpful :smile:


Remember you aren’t actually expected to know these explanations at A level, so don’t quote them in an exam. But I am glad to hear it had been helpful.
Reply 6
Original post by har6547
ok thank you. What about covalent character in ionic bonds, why does that increase bond strength?


ionic bonds may exhibit covalency:
Experiemental value of the lattice
enthalpy of ionic bonds may be higher
than expected (theoretical) due to the
ionic compound exhibiting covalency due
to the small size of the cation & the large size of the anion. This allows the small
cation to have a strong enough electro
-negativity to draw the anion’s electron cloud towards itself

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