The Lewis structure of hydrogen cyanide (HCN) consists of hydrogen (H), carbon (C), and nitrogen (N). Carbon uses one of its valence electrons to form a single covalent bond with hydrogen on one side. The remaining three valence electrons combine with those of nitrogen to form a triple covalent bond on the other side. Carbon does not have any lone pairs to repel nitrogen’s lone pairs. Therefore, hydrogen and nitrogen are at the molecule’s opposite ends, resulting in a linear geometry with a bond angle of 180 degrees.

Nitrogen is highly electronegative and will attract the shared electron pairs toward itself. As a result, it will acquire a partial negative charge. On the other hand, hydrogen is less electronegative than carbon. It will acquire a partial positive charge due to unequal electron sharing. Therefore, HCN is a polar molecule with a dipole moment vector directed from hydrogen to nitrogen.