Descibe how electronegativity and molecular shape determine the polarity of a molecule. Then describe why chemists consider relative electronegativity values and not absolute electronegativity values when determining the polarity of a bond. Also explain how a molecule with polar bonds can be non-polar overall.

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Explanation:

Electronegativity is an idea put forward by Linus Pauling to explain the fact that in a molecule, one atom may attract the shared electrons of the bond closer to itself than the other.

Hence electronegativity is defined as the power of an atom in a molecule to attract electrons to itself.

Pauling originally described electronegativity as a relative quantity. It depends on the electronegativities of the atoms in the molecule. However, some methods have sought to measure the absolute electronegativity of a free atom.

A bond is polar when the atoms that make up the bond have a significant difference between the atoms of the molecule.

However, a molecule may possess polar bonds but may not have an overall dipole moment owing to the shape of the molecule.

For instance, CCl4 has four polar C-Cl bonds but the overall molecule is non polar because due to the fact that the molecule is tetrahedral in shape and highly symmetrical hence the individual dipoles cancel out.

catya your not at all which answer i've seen you do this on another question!

the formula mass of a molecule or a compound is the sum of the atomic weights of the atoms in its empirical formula

(that's what i know about formula mass)