Why is CO2 and CCl4 are both nonpolar even though they contain polar bonds?

Answer 1

C=O bonds are polar, but polarity is the uneven distribution of charge ACROSS A MOLECULE, when there is one side slightly negative, and then the other side is slightly negative, the whole molecule is slightly negative, so it's not polar. In other words, the centre of the negative charge is in the same place as the centre of positive charge, and they cancel each other out.

Same story for CCl4, even tho it's not linear, the chlorines are mirror imaged on the other side of the carbon, just like the oxygen is mirror imaged on the other side of the carbon in CO2. The charges are cancelled out, same story for both molecules.

Answer 2

While CO2 and CCl4 both have polar bonds (C=O and C-Cl, respectively), their molecular geometry leads to a symmetrical distribution of the polar bonds, resulting in a net dipole moment of zero. In CO2, the two O atoms pull electron density equally, canceling out the individual dipoles. In CCl4, the four Cl atoms point towards the corners of a tetrahedron, resulting in a symmetrical, nonpolar molecule.