Atoms Join Up
How atoms combine to form molecules
What this lesson covers
Why it matters
Imagine two lonely magnets snapping together with a satisfying click. Atoms do the same, but with an invisible chemical handshake.
Predict first
When two hydrogen atoms join to form a molecule, what actually changes?
A molecule is a new chemical entity. While the atoms remain, their combined behavior is distinct from the individual atoms.
- The atoms disappear and turn into energy
- They form a new substance with different properties — correct
- They just sit next to each other without touching
What you do
Bond two hydrogen atoms together. Each H has a valency of 1, so they share one pair of electrons to form a single H–H bond — one molecule of H₂.
Check yourself
Which statement best defines a molecule?
A molecule is the smallest particle of a substance (element or compound) that can exist independently and still shows its chemical properties. Most are made of two or more atoms joined by chemical bonds (for example, H₂ has two hydrogen atoms).
If you break a water molecule (H₂O) apart, what do you get?
Chemical bonds hold atoms together. Breaking the molecule separates the constituent atoms, which may then form other substances.
- A mixture of two different elements
- The smallest particle of a substance that can exist independently — correct
- A single atom that has gained electrons
- Hydrogen and Oxygen atoms — correct
- Smaller pieces of water
- Nothing, because molecules are solid