Hydrogen bonds form when a hydrogen atom, which is covalently bonded to a highly electronegative atom, interacts with another electronegative atom. The key electronegative atoms involved in this process typically include nitrogen (N), oxygen (O), and fluorine (F).
To elaborate, the highly electronegative atom creates a partial negative charge, which attracts the partial positive charge of the hydrogen atom. This attraction is what constitutes a hydrogen bond. For example, in water (H2O), the oxygen atom is highly electronegative and pulls the shared electrons closer, making the hydrogen atoms slightly positive. When these hydrogen atoms come close to other electronegative atoms like oxygen or nitrogen in different molecules, hydrogen bonds can form, playing a critical role in determining the properties of substances, such as the high boiling point of water.