In molecular chemistry, which of the following bond formulas represents a polar molecule with an uneven sharing of electrons between the bonded atoms?

Introduction / Context:
Polarity of molecules and bonds is an important concept in chemistry because it affects solubility, boiling points, and reactivity. A polar bond arises when two atoms with different electronegativities share electrons unequally, giving one end of the bond a partial negative charge and the other a partial positive charge. This question asks which of several simple bonds forms part of a polar molecule. Understanding electronegativity differences helps you predict which bonds are polar.

Given Data / Assumptions:
- The bonds listed are carbon oxygen, carbon nitrogen, and hydrogen nitrogen. - We must identify which of these represents a polar molecule or polar bond. - We assume typical electronegativity values on the Pauling scale.

Concept / Approach:
A bond is polar if there is a significant electronegativity difference between the two bonded atoms. Oxygen and nitrogen are more electronegative than carbon and hydrogen. In a C O bond, oxygen pulls electron density more strongly than carbon, making the bond polar. Similarly, in a C N bond, nitrogen is more electronegative than carbon, and in an H N bond, nitrogen is more electronegative than hydrogen. Therefore, all three bonds listed are polar. The correct answer should therefore include all of them together.

Step-by-Step Solution:
Step 1: Compare electronegativities for carbon and oxygen. Oxygen is significantly more electronegative, so the C O bond is polar with oxygen partially negative. Step 2: Compare electronegativities for carbon and nitrogen. Nitrogen is more electronegative than carbon, so the C N bond is also polar. Step 3: Compare electronegativities for hydrogen and nitrogen. Nitrogen again is more electronegative, so the H N bond is polar with nitrogen carrying partial negative charge. Step 4: Since all three bonds involve atoms with different electronegativities and unequal sharing of electrons, they are all polar bonds. Step 5: Conclude that All of the above is the correct answer.

Verification / Alternative check:
You can verify this by checking approximate electronegativity values. Carbon is around 2.5, nitrogen around 3.0, oxygen around 3.5, and hydrogen around 2.1. The differences between carbon and oxygen, carbon and nitrogen, and hydrogen and nitrogen are all large enough to create polar bonds. These polar bonds often lead to polar molecules when the molecular geometry does not cancel the dipole moments. For example, the molecules formaldehyde and ammonia both contain such polar bonds and have overall dipole moments.

Why Other Options Are Wrong:
Option A includes only the C O bond, which is polar, but it ignores the fact that the other listed bonds are also polar. Option B focuses only on the C N bond, again a polar bond, but not the only one with unequal electron sharing. Option C focuses only on the H N bond, which is polar, but omits the others, so it is incomplete.

Common Pitfalls:
Students may think that only bonds with very large electronegativity differences, such as those involving metals and nonmetals, are polar. However, even differences between nonmetals like carbon, nitrogen, oxygen, and hydrogen can produce noticeable polarity. Another pitfall is confusing polar bonds with polar molecules. A molecule may contain polar bonds yet be nonpolar overall if its geometry is symmetrical and dipoles cancel. In this question, the focus is on the bonds themselves, not on whole molecule symmetry.

Final Answer:
The correct answer is: All of the above.