Chemical Bonding — Basic Concepts: Which is the Most Polar Bond?
Question
Which is the most polar bond?
- C–C
- C–H
- N–H
- O–H
- Se–H
Show/Hide Answer
d. O-H is the most polar bond.
Refer to:
Strategy Map
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| Strategy Map Steps |
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| 1. Assign your electronegativity values (use the Pauling Electronegativity values from Figure 4.3.3: Electronegativity Value Chart (1)). |
2. Identify the electronegativity difference between the elements forming the bond.
Show/Hide HintTo do this, subtract the larger value from the smaller value. |
| 3. Identify which bond has the highest difference; that will be the most polar bond. |
Solution
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C–C
- Electronegativity difference = 0
C–H
- C electronegativity = 2.5
- H electronegativity = 2.1
- Electronegativity difference = 0.4
N–H
- N electronegativity = 3.0
- H electronegativity = 2.1
- Electronegativity difference = 0.9
O–H
- O electronegativity = 3.5
- H electronegativity = 2.1
- Electronegativity difference = 1.4
Se–H
- Se electronegativity = 2.4
- H electronegativity = 2.1
- Electronegativity difference = 0.3
Answer: O-H has the largest electronegativity difference between the bonded atoms, so it is the most polar bond.
Guided Solution
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The guided solution below will give you the reasoning for each step to get your answer, with reminders and hints.
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| Guided Solution Ideas |
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This question is a theory type problem that asks us to evaluate the covalent bonds between the elements given. We are asked to determine the most polar bond, which will be the bond with the most unequal electron distribution.
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The question asks you to identify which of the given bonds is the most polar, what property relates to this?
Show/Hide Think About This!Electronegativity is a measure of the tendency of an atom to attract electrons or electron density. Which bond has the highest electronegativity difference? |
Recall that polar covalent bonds have an electronegativity difference between the bonded atoms.
Show/Hide Think About This!For this type of bond to occur, the difference guideline must be between 0.4 and 1.8. Within this range, the higher the difference, the more polar the bond. Refer to 4.3.5: Electronegativity and Bond Type (1). |
| Complete Solution |
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C–C
C–H
N–H
O–H
Se–H
Difference less than 0.4, so the bond is nonpolar. The bond with the highest electronegativity difference is between O and H; therefore, it is the most polar bond. Answer: O-H has the most polar bond. Show/Hide Think About This!For all bonds except C-C, one of the atoms is H, so you can focus on the change in electronegativity of the atom H is bound to. If you rank these atoms from highest to lowest electronegativity, you will predict which bond with H will be the most polar. |
Check Your Work
The most electronegative atom bound to H above is O, with an electronegativity of 3.5, so we would predict that O-H would be the most polar bond in the list.
Show/Hide Think About This!
Electronegativity ranking from largest to smallest: O > N > Se > C
Does your answer make chemical sense?
Show/Hide Answer
The more electronegative an atom is, the stronger the attraction between its nucleus and outside electrons will be. Atoms that are smaller will have higher electronegativities as there are fewer electrons to shield the nucleus from this attraction. Oxygen is one of the most highly electronegative elements as its nucleus forms a very strong attraction to outside electrons, such as with a hydrogen atom.
PASS Attribution
- LibreTexts PASS Chemistry Book CHEM 1500 (2).
- Question 4.E.20 from LibreTexts PASS Chemistry Book CHEM 1500 (3) is used under a CC BY-NC-SA 4.0 license.
- Question 4.E.20 is from a question in Section 7.E.2: 7.3: Covalent Bonding from LibreTexts Chemistry 1e (OpenSTAX) (4), which is under a CC BY 4.0 license.
- The question in Section 7.E.2: 7.3: Covalent Bonding is question 20 from OpenStax Chemistry 2e (5), which is under a CC BY 4.0 license. Access for free at https://openstax.org/books/chemistry-2e/pages/1-introduction.
References
1. OpenStax. 4.3: Covalent Bonding. In CHEM 1500: Chemical Bonding and Organic Chemistry. LibreTexts, 2023. https://chem.libretexts.org/Courses/Thompson_Rivers_University/CHEM_1500%3A_Chemical_Bonding_and_Organic_Chemistry/04%3A_Chemical_Bonding_I-_Basic_Concepts/4.03%3A_Covalent_Bonding.
2. Blackstock, L.; Brewer, S.; Jensen, A. PASS Chemistry Book CHEM 1500; LibreTexts, 2023. https://chem.libretexts.org/Courses/Thompson_Rivers_University/PASS_Chemistry_Book_CHEM_1500.
3. Blackstock, L.; Brewer, S.; Jensen, A. 4.1: Question 4.E.20 PASS – Which Is the Most Polar Bond? In PASS Chemistry Book CHEM 1500. LibreTexts, 2023. https://chem.libretexts.org/Courses/Thompson_Rivers_University/PASS_Chemistry_Book_CHEM_1500/04%3A_Chemical_Bonding_I_-_Basic_Concepts/4.01%3A_Question_4.E.20_PASS_-_which_is_the_most_polar_bond.
4. OpenStax. 7.E: Chemical Bonding and Molecular Geometry (Exercises). In Chemistry 1e (OpenSTAX). LibreTexts, 2023. https://chem.libretexts.org/Bookshelves/General_Chemistry/Chemistry_1e_(OpenSTAX)/07%3A_Chemical_Bonding_and_Molecular_Geometry/7.E%3A_Chemical_Bonding_and_Molecular_Geometry_(Exercises).
5. Flowers, P.; Theopold, K.; Langley, R.; Robinson, W. R. Ch. 7 Exercises. In Chemistry 2e; OpenStax, 2019. https://openstax.org/books/chemistry-2e/pages/7-exercises.
