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For exercise 3.77 in 6th edition, CO2 has more ionic character than CS2. Why does CO2 have more ionic character ? I know Sulfur is below C but why does that mean it has less of a difference in electronegativity with C than O does ? C and O are in the same row and wouldn't that make them more similar than C and S which are in a different group and a different period ?
For this problem, you should only be comparing the O to the S since C is present in both molecules. We know that the S has a larger atomic radius because it is lower in the group. Elements with bigger radii have a lower electron affinity and therefore a lower electronegativity. Because of this fact, the S has a greater polarizability than the O (S electrons are attracted to the C nucleus more than the C electrons are) making CO2 less covalent and thus more ionic.
As you go down a group, atomic radius increases, so there is less pulling power on the electrons. CO2 is more ionic because oxygen is in the second period so its atomic radius is small which means there is more pulling on the elctrons by the nucleus. Therefore, Oxygen is very high in electronegtivity compared to Sulfur. So the difference in electronegativity is higher between C and O than C and S
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