Atoms of elements at the top of a group on the periodic table are smaller than Atoms of elements at the bottom of the group how does this help explain the difference in reactivity of metals within a group

Which of the following is not a characteristic of a hydrogen bond? 1. it is responsible for the unusual physical properties of water. 2. it is weaker than a covalent bond. 3. it is stronger than other dipole-dipole interactions. 4. it can occur when hydrogen is covalently bound to very electronegative elements liks f, cl, br and i.