Molecular Polarity Practice Is HCN a polar covalent molecule or a nonpolar covalent molecule? N
The Correct Answer and Explanation is:
Correct Answer: HCN is a polar covalent molecule.
Explanation:
HCN stands for hydrogen cyanide, which consists of three atoms: hydrogen (H), carbon (C), and nitrogen (N). To determine whether HCN is a polar covalent molecule or a nonpolar covalent molecule, we analyze both the bond polarity and the overall molecular shape.
First, let us consider the bonds within the molecule. The structure of HCN is linear with the atoms connected in the sequence H-C≡N. The carbon and nitrogen atoms share a triple bond, and carbon and hydrogen share a single bond. The electronegativities of these atoms are different: hydrogen is approximately 2.1, carbon is 2.5, and nitrogen is 3.0. The difference in electronegativity between the atoms leads to polar bonds. The C≡N bond is particularly polar because of the significant electronegativity difference between carbon and nitrogen.
Second, we examine the geometry of the molecule. HCN is a linear molecule, meaning all three atoms lie along a straight line. Despite being linear, the unequal sharing of electrons results in a dipole moment. Nitrogen, being the most electronegative atom, pulls electron density toward itself, creating a partial negative charge at the nitrogen end and a partial positive charge at the hydrogen end.
For a molecule to be nonpolar, either all bond dipoles must cancel out or there must be an even distribution of electron density. In the case of HCN, the dipole moments do not cancel because one end of the molecule (the nitrogen side) is more electronegative, creating an uneven distribution of charge.
In conclusion, HCN has polar bonds and an overall molecular dipole, making it a polar covalent molecule. Its linear shape does not eliminate polarity because of the significant electronegativity difference between nitrogen and the other atoms.
