VSEPR Theory: Investigating Ionic Molecules

[Tanya Back]

Vsepr Theory

Hey Guys! How are u guys doing today?

I was wondering how do we know dat BeF2 is polar?..i drew it out by using the VSEPR theory..but what confuses me is dat BeF2 ionic..can we still use VSEPR theory to draw it out?

Tanya

Thank you in advance!

 

[Tanya Back]

Oh Silly me! Ionic bonds are polar bonds.. opps!

 

[maverick280857]

Strictly speaking, there is nothing that is "ionic". Its a tradeoff between the ionic character and the covalent character that a molecule has. Something that is largely covalent (such as water for example) is usually passed off as a covalent compound as it predominantly behaves so.

Your question was, how do we know that berrylium fluoride is polar. Well, from the VSEPR theory, BeF2 turns out to be linear and it cannot be polar. There are of course bond dipoles but they are oriented antiparallel to each other which makes the net dipole moment of the molecule zero.

If you were asked to find out whether a given substance is covalent or ionic, you would (in theory) calculate its percentage ionic character from a knowledge of the measured dipole moment and the dipole moment for 100% ionic character. This would tell you to what degree is the substance ionic (or covalent).