Are hydrogen bonds weak or strong?

Strong.

Strong

Hydrogen bonds are relatively weak compared to covalent or ionic bonds, but they are still stronger than other types of intermolecular attractions such as Van der Waals forces. To understand why hydrogen bonds are considered relatively strong, let me explain how they form.

Hydrogen bonds occur when a hydrogen atom is covalently bonded to a highly electronegative atom (typically nitrogen, oxygen, or fluorine) and is also attracted to another electronegative atom nearby. The hydrogen atom behaves like a bridge between the two electronegative atoms. The partial positive charge on the hydrogen attracts the partial negative charge on the other atom, resulting in the formation of a hydrogen bond.

The strength of a hydrogen bond is determined by several factors, including the electronegativity difference between the hydrogen atom and the electronegative atom, the distance between the two atoms involved in the bond, and the presence of any additional influencing factors such as solvent effects.

In general, hydrogen bonds are weaker than covalent or ionic bonds because they involve weaker electrostatic interactions. However, they can still have significant effects on the physical and chemical properties of molecules. For example, hydrogen bonding is responsible for the unique properties of water, such as its relatively high boiling and melting points compared to similar-sized molecules.

So, to summarize, hydrogen bonds are relatively weak compared to covalent or ionic bonds, but they are still stronger than other intermolecular attractions. Their strength is determined by factors such as electronegativity, distance, and environmental conditions.