Coefficients vs. Subscripts: The Basics
In chemistry, a coefficient is a large number placed in front of a chemical formula that indicates the number of molecules or moles of that substance. A subscript is a small number written after an element's symbol that indicates the number of atoms of that element within a single molecule.
Section 2: The Role of a Coefficient
Coefficients multiply the entire molecule that follows them. They are primarily used to balance chemical equations, ensuring that the number of atoms of each element is the same on both the reactant and product sides, thus upholding the law of conservation of mass. If no coefficient is written, it is assumed to be one.
Section 3: A Practical Example: Water (H₂O)
In the formula for water, H₂O, the subscript '2' after the 'H' means there are two hydrogen atoms in one water molecule. If you see '3H₂O', the coefficient '3' means you have three separate water molecules. This amounts to a total of six hydrogen atoms (3 × 2) and three oxygen atoms (3 × 1).
Section 4: Why the Distinction is Critical
The distinction is fundamental. Changing a subscript changes the chemical identity of the substance; for example, H₂O is water, but changing the subscript to H₂O₂ creates hydrogen peroxide, a completely different compound. In contrast, changing a coefficient only changes the quantity of the substance, not what it is.