Atomicity is a simple but frequently tested concept in Class 9 Chemistry (Atoms and Molecules chapter).
Atomicity: Number of atoms in one molecule.
Diatomic: H₂, O₂, N₂ (atomicity = 2).
Triatomic: O₃ Ozone (atomicity = 3).
Polyatomic: P₄ (4), S₈ (8).
Atomicity is defined as the total number of atoms present in one molecule of an element or compound.
In simple terms: count how many atoms are bonded together to form one molecule of the substance.
| Molecule | Atomicity | Name |
|---|---|---|
| Noble gases (He, Ne, Ar) | 1 | Monoatomic |
| H₂, O₂, N₂, Cl₂, F₂ | 2 | Diatomic |
| O₃ (Ozone) | 3 | Triatomic |
| P₄ (Phosphorus) | 4 | Tetraatomic |
| S₈ (Sulphur) | 8 | Polyatomic |
Most asked in exams:
Atomicity is the number of atoms present in one molecule of an element. Examples: H₂ has atomicity 2 (diatomic), O₃ (ozone) has atomicity 3 (triatomic), P₄ has atomicity 4, and S₈ has atomicity 8 (polyatomic).
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