Understanding the concept:
- The number of atoms that make up a molecule of an element is expressed as its atomicity.
- For instance, the ozone molecule () has an atomicity of three since it contains three oxygen atoms.
Classification of atomicity on the basis of the number of atoms in a molecule:
- Monoatomic molecules with only one atom, such as xenon ().
- Diatomic Two atoms make up a diatomic molecule, such as oxygen ().
- Triatomic molecules have three atoms, such as ozone ().
- Tetratomic molecules have four atoms, such as phosphorus ().
- A polyatomic molecule is one with more than four atoms, such as sulfur ().