Hydrogen Bonding
Hydrogen bonds link H to N, O or F on neighbouring molecules.
About this topic
A hydrogen bond is a strong dipole–dipole attraction between a hydrogen atom bonded to N, O or F and a lone pair on another N, O or F atom. It explains the unusually high boiling point of water, the lower density of ice, the structure of DNA and the folding of proteins.
The effect happens because N, O and F are so electronegative that the hydrogen is left with a strong partial positive charge and almost no electron cloud, so it can approach the lone pair of a neighbouring molecule closely. Each hydrogen bond has about a tenth of the strength of a covalent bond, yet there are huge numbers of them. In ice, each water molecule bonds to four others in an open hexagonal lattice, which takes up more space than liquid water, so ice floats.
Water would boil at around minus 80 degrees Celsius without hydrogen bonding, and Earth would have no liquid oceans. In DNA, hydrogen bonds join the base pairs A to T and G to C, holding two strands together but allowing them to unzip for copying. Plant sap rises through tall trees thanks to water's cohesion.
A common mistake is calling hydrogen bonds true bonds within molecules; they are intermolecular. Also, not every compound containing hydrogen forms them; methane does not, because carbon is not electronegative enough.
Key ideas
- Explains ice floating
- High surface tension
- Holds DNA strands together
Quick check
Use cases: where Hydrogen Bonding helps
- Homework: review the key idea behind Hydrogen Bonding before you start a problem set.
- Exam revision: use the quick check to test whether you can recall Hydrogen Bonding without notes.
- Visual learning: play with the interactive lab to see how Hydrogen Bonding changes when you adjust its inputs.
- Teaching a friend: explain Hydrogen Bonding in your own words, then compare your version with the key ideas.
Chemistry explains medicine, food, cleaning products, fuels and building materials.
Frequently asked questions
What is Hydrogen Bonding?
Hydrogen bonds link H to N, O or F on neighbouring molecules.
What will I learn in Hydrogen Bonding?
Explains ice floating. High surface tension. Holds DNA strands together.
Is Hydrogen Bonding part of Chemistry?
Yes. It is one of 150 Chemistry topics on LearnViz HighSchoolEdu, with 3 key ideas, a live animation and a quick check.
Does the Hydrogen Bonding lab work on a phone or tablet?
Yes. The animation resizes to fit your screen and supports touch, so you can drag, tap and slide with your finger.
How should I study Hydrogen Bonding?
Read the summary and key ideas first, play with the interactive lab to see the idea in motion, then answer the quick check. If you get a question wrong, go back to the key idea it tests.
Do I need an account, and is my progress saved?
No account is needed. Marking a topic as learned is saved in your own browser, so it stays on that device and is not sent to a server.