Subscripts
* What they indicate: The number of atoms of a particular element within a molecule or formula unit.
* Location: They appear *below and to the right* of an element's symbol.
* Example: In H₂O (water), the subscript "2" after the "H" tells us there are two hydrogen atoms in each water molecule.
Coefficients
* What they indicate: The number of molecules or formula units of a substance in a chemical reaction.
* Location: They appear *in front* of a chemical formula.
* Example: In the reaction 2H₂ + O₂ → 2H₂O, the coefficient "2" in front of H₂ means two molecules of hydrogen gas are involved, while the "2" in front of H₂O indicates that two water molecules are produced.
In Summary
* Subscripts: Tell us the *internal* structure of a molecule or formula unit (how many of each atom).
* Coefficients: Tell us the *number* of molecules or formula units involved in a reaction.
Think of it this way:
* Subscripts are like the ingredients in a recipe. They tell you how much of each ingredient you need to make *one* batch of the recipe.
* Coefficients are like the number of times you need to make the recipe. They tell you how many *batches* you're preparing.
