As we know that Polarity exists due to presence of charges. And charges are generated in molecules due to Electronegativity differences. The element with higher electronegativity will have partial negative charge, while element with less electronegativity will have partial positive charge. This partial positive and partial negative charge on a molecule makes it polar.
Polarity mainly depends upon the shape of a molecule. For example, In water Oxygen being more electronegative is partial negative and Hydrogen being less electronegative is partial positive. It is polar and has a bent structure. It means the two bond moments are not cancelling each other hence the water molecule has a net dipole moment of 1.84 D.
Secondly, CO₂ (Carbon dioxide) also has a more electronegative Oxygen atom and less electronegative Carbon atom. In this case the net dipole moment on CO₂ is zero. This is because the structure of CO₂ is linear. As the two dipoles being equal and opposite cancel out the effect of each other making the CO₂ molecule non-polar.
