There’s a reason ice floats in the water, and that reason is called the hydrogen bond.
According to that portrait, a hydrogen bond forms when a hydrogen atom, which is already stably integrated into a molecule, is attracted to a highly electronegative atom. This taste to suck electrons and become ions (electrically charged particles, in this case of negative charge), binds them to oxygen, nitrogen, and fluoride atoms. Let’s look at an example.
Ice is less dense than liquid water because, when water molecules are cold and still, weak hydrogen bonds constantly keep them at a fixed distance. However, in free-flowing water, the links are continually breaking and remaking, due to the attraction, we mentioned earlier.
This is all great, but that traditional image also implies a range of hydrogen bond strength. However, over the past 40 years, much evidence has emerged about weaker bonds, including hydrogen and carbon, which is not very electronegative.
Six years ago, IUPAC formed a committee to clear up the confusion. It concludes that hydrogen bonding is a much more embedded entity than previously thought, and a new definition is needed. One that combats the misconception, widespread among chemists, about when and where hydrogen bonds can occur and encourage them to consider the influence of that link in new situations.
This will help us to detach ourselves from the current dependence on expensive and toxic catalysts containing precious metals and move forward on the path of getting cheaper and greener alternatives based on organic compounds.