Madeline K. answered • 10/18/21
B.A. in Chemistry with 3+ years of Tutoring Experience
Here are is how to determine the polarity of a covalent bond:
Background info: Look at a periodic table, preferably one with the Pauling electronegativity values listed on each element for a problem like this. Electronegativity of atoms increases from left to right, and increases from bottom to top. The noble gasses (He, Ne, etc) are excluded from this (they are already fully "happy" with the number of valence electrons they have), so the MOST electronegative element in the periodic table is F, Fluorine. The Pauling electronegativity values give an actual number value to how electronegative each element is,
How to compare covalent bond polarities:
1.) Find both elements Pauling electronegativity values on the periodic table(the higher the value, the more electronegative, with Fluorine having a pauling value of about 4).
-For example, if looking at a bond between C and F, C has a pauling value of about 2.5 and F has a pauling value of about 4.
2) Find the difference between the two electronegativities of the two elements in the covalent bond by subtracting the smaller number from the larger number. That difference you calculate represents how polar the bond is (aka how different the two electronegativities of the elements are), and the larger this number is, the more polar the bond is. Using the example above, the number you would get to represent how polar the C-F bond would be is 4 - 2.5 which = 1.5. If we were to compare this to a C-O bond, we would calculate 3.5 (Oxygen pauling value) - 2.5 (carbon pauling value) and would get 1. This is smaller than 1.5, meaning that a C-O bond is LESS polar than a C-F bond.
3) If you are comparing multiple bonds, you can repeat steps 1 and 2 for each to calculate the polarity of each bond and see which one is the most polar.
Hope this helps! Feel free to reach out if you need more chemistry help and would like to schedule an online tutoring session!
