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What holds two atoms together, and how hard do you have to shake them to break it?
Molecular Bonding lab · Last updated: 16 October 2026
You join two atoms into a molecule, then shake them harder and harder to see what it takes to pull them apart. They find out that atoms are held together by shared electrons, and that heat is really just shaking. It explains why some substances melt or break down easily and others are incredibly tough.
What you'll discover
- In a covalent bond two atoms share a pair of electrons, and both nuclei are attracted to that shared pair.
- Bonded atoms are always vibrating, and heating makes them vibrate harder.
- Breaking a bond takes energy, and double and triple bonds take more energy to break than single ones.
The science in plain words
Atoms are made of a positive nucleus surrounded by negative electrons. When two atoms come close, their electrons can be attracted to both nuclei at once. In a covalent bond, two atoms share a pair of electrons, and the attraction of both nuclei to that shared pair holds them together. Hydrogen gas, water and the carbon compounds in living things are held together this way. Atoms can also share two or three pairs, making double and triple bonds, which are shorter and stronger.
Another kind of bond forms when one atom gives electrons to another, making a positive ion and a negative ion that attract each other. This is an ionic bond, as in common salt.
A bond is not rigid. The two atoms behave as if joined by a spring, constantly vibrating closer and further apart. Temperature is a measure of how vigorously particles move, so heating makes them vibrate harder. Breaking a bond takes a definite amount of energy, called the bond energy. If the vibrations become violent enough, the atoms fly apart. This is why some compounds break down when heated strongly. Nitrogen gas, with its triple bond, is extremely hard to break apart, which is why the nitrogen that makes up most of the air is so unreactive.
Where it fits
Common questions
What is a covalent bond?
A covalent bond forms when two atoms share a pair of electrons. Both atoms' nuclei are attracted to the shared electrons, and this attraction holds the atoms together. Water, oxygen gas, methane and most of the molecules in living things are held together by covalent bonds.
What is the difference between ionic and covalent bonds?
In an ionic bond one atom transfers electrons to another, forming oppositely charged ions that attract each other, as in sodium chloride. In a covalent bond the atoms share electrons instead. Ionic compounds usually have high melting points and conduct electricity when dissolved.
Does breaking a chemical bond release energy?
No. Breaking a bond always takes energy. Energy is released when new bonds form. In reactions such as burning, the new bonds formed release more energy than was needed to break the old ones, so overall the reaction gives out heat.
Related labs
- Atomic Orbitals: Where is the electron? Look for it again and again, and a shape appears.
- Polymer Chains: Plastics are long chains of small molecules. Why does a chain curl up, and why is it stretchy?
- Chemical Reactions: Molecules must crash hard enough to react. What makes that happen more often?
See all chemistry labs or every Taz science lab.
Try it yourself
The Molecular Bonding lab is one of the interactive 3D science labs inside Taz. Change one thing, predict what will happen, then run it and watch. Labs open after you sign in.