Chemistry Question

[Tawantinsuyu]

How do you identify a molecule as polar covalent or non-polar covalent without knowing the EN values? Aren't closer molecules on the periodic table usually non-polar? But how close?

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[Oso]

Remember that on the periodic table, electronegativity increases going from left to right, and going up (so F is the most electronegative). If two atoms in a covalent bond are the same or have roughly the same electronegativity (ex. H and C), these will be non-polar covalent bonds. If there's a big difference in electronegativity, you'll most likely have a polar covalent bond (ex. H and O). Polar covalent bonds will result in dipoles, and you can look at the overall molecular geometry to determine if the dipoles cancel out or not. So CF4 has four polar covalent bonds, but the dipoles all cancel out so there's no net polarity. HCl has one polar covalent bond --> one net dipole --> the molecule is polar.

 

[Tawantinsuyu]

Remember that on the periodic table, electronegativity increases going from left to right, and going up (so F is the most electronegative). If two atoms in a covalent bond are the same or have roughly the same electronegativity (ex. H and C), these will be non-polar covalent bonds. If there's a big difference in electronegativity, you'll most likely have a polar covalent bond (ex. H and O). Polar covalent bonds will result in dipoles, and you can look at the overall molecular geometry to determine if the dipoles cancel out or not. So CF4 has four polar covalent bonds, but the dipoles all cancel out so there's no net polarity. HCl has one polar covalent bond --> one net dipole --> the molecule is polar.

Thanks!!!

 

[Ismet]

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