Why fluorine is more electronegative than chlorine

Forum Organic Chemistry Fluorine is more electronegative than Fluorine is more electronegative than chlorine but the electron affinity of chlorine is more than that of fluorine. Shreya, 4 years ago. Enter email id Enter mobile number. Cancel Notify me. Other Related Questions on Organic Chemistry. How we can prepare 0. Dilute 12 M HCL solution to. View all Questions ». You will get reply from our expert in sometime.

We will notify you when Our expert answers your question. To View your Question Click Here. View courses by askIITians. Click Here Know More. Full Name. The electrons are actually in a sigma orbital, and are moving constantly within that orbital. That means that fluorine attracts the bonding pair much more strongly than carbon does. The bond - on average - will look like this:. The bonding pair is in the second energy level of both carbon and fluorine, so in the absence of any other effect, the distance of the pair from both nuclei would be the same.

The electron pair is shielded from the full force of both nuclei by the 1s electrons - again there is nothing to pull it closer to one atom than the other. BUT, the fluorine nucleus has 9 protons whereas the carbon nucleus has only 6. It is this extra nuclear charge which pulls the bonding pair on average closer to the fluorine than the carbon. The bonding pair of electrons will be dragged towards the chlorine but not as much as in the fluorine case. Chlorine isn't as electronegative as fluorine.

In the chlorine case, the bonding pair will be shielded by all the 1-level and 2-level electrons. That is the same as the pull from the fluorine, but with chlorine the bonding pair starts off further away from the nucleus because it is in the 3-level.

Since it is further away, it feels the pull from the nucleus less strongly. Think about the carbon-fluorine bond again. Because the bonding pair is pulled towards the fluorine end of the bond, that end is left rather more negative than it would otherwise be. The carbon end is left rather short of electrons and so becomes slightly positive. We describe a bond having one end slightly positive and the other end slightly negative as being polar.

An atom like fluorine which can pull the bonding pair away from the atom it is attached to is said to have a negative inductive effect. Most atoms that you will come across have a negative inductive effect when they are attached to a carbon atom, because they are mostly more electronegative than carbon.

You will come across some groups of atoms which have a slight positive inductive effect - they "push" electrons towards the carbon they are attached to, making it slightly negative. Bromine and the other halogens are all more electronegative than hydrogen, and so all the hydrogen halides have polar bonds with the hydrogen end slightly positive and the halogen end slightly negative.

The polarity of these molecules is important in their reactions with alkenes. Bromine is more electronegative than carbon and so the bond is polarised in the way that we have already described with C-F and C-Cl. The very electronegative oxygen atom pulls both bonding pairs towards itself - in the sigma bond and the pi bond.

That leaves the oxygen fairly negative and the carbon fairly positive. Jim Clark Chemguide.