Let's learn about electronegativity in A-Level Chemistry and see how it affects bonding!
Electronegativity is the ability to attract the bonding electrons in a covalent bond
Atoms with strong electron pulling power in covalent bonds are said to be highly electronegative.
Fluorine is the most electronegative element. Oxygen, nitrogen chlorine are also strongly electronegative.
In a covalent bond between two atoms of different electronegativities, the bonding electrons are pulled
towards the more electronegative atom. This makes the bond polar.
The covalent bonds in diatomic elements are non-polar because the atoms have equal electronegativities. Electrons are equally attracted to both nuclei.
In a polar bond the difference in electronegativity between the two atoms causes a dipole.
A dipole is a difference in charge between the two atoms causes by a shift in electron density in the bond.
The greater the difference in electronegativity between two atoms, the more polar the bond will be.
Shape and polarity
Whether a molecule has a permanent dipole depends on its shape and the polarity of its bonds.
1. In a simple molecule, like hydrogen bromide, the polar bond gives the whole molecule a permanent dipole –it’s a polar molecule.
2. A more complicated molecule may have several polar bonds. If the polar bonds are arranged so they point in opposite directions, they’ll cancel each other out. The molecule is non-polar overall.
3. If the polar bonds all point in roughly the same direction, then the molecule is polar
4. Lone pairs of electrons on the central atom also have an effect on the overall polarity and may cancel out the dipole created by the bonding pairs.
Drafted by Eunice (Chemistry)
References
https://chem.libretexts.org/Courses/Oregon_Institute_of_Technology/OIT%3A_CHE_202_-_General_Chemistry_II/Unit_5%3A_The_Strength_and_Shape_of_Covalent_Bonds/5.2%3A_Molecular_Shape
http://biochemhelp.com/how-to-predict-polarity-of-molecules-based-on-their-shape.html