How many atoms are represented?

KBr

C12H22O11

KAlSi3O8

Ag3PO4

CH3CO2C6H4COOH

An atom is the smallest indivisible particle that takes part in any chemical reaction. They are easily identified distinctively as elements in a compound.

The subscripts accompanying a chemical symbol shows the number of atoms of elements combining to give a compound:

Compound Elements Number of atoms

KBr K Br 2

C₁₂H₂₂O₁₁ 12 (C) 22 (H) 11 (O) 12 + 22 + 11 = 45

KAlSi₃O₈ 1 (K) 1 (Al) 3 (Si) 8 (O) 1 + 1 + 3 + 8 = 13

Ag₃PO₄ 3 (Ag) 1 (P) 4 (O) 3 + 1 + 4 = 8

CH₃CO₂C₆H₄COOH 9 (C) 8 (H) 4 (C) 9+8+4 = 21