What is the strongest evidence for hydrogen bonding?
1. Hydrogen is able to accept or donate electrons, so it is the most versatile atom in the periodic chart.
2. Hydrogen can be considered either a metal or nonmetal.
3. The boiling points of NH3, H2O, and HF are abnormally high compared with the rest of the hydrides in their respective periods.
4. Hydrogen has an extremely low electronegativity.