Diagrams.ink / Chemistry note

Balance by counting molecules, never by changing them

Atoms are never created or destroyed in a reaction, so every element must appear the same number of times on both sides. Add or remove whole molecules with the coefficients and watch the atom counts follow.

Ball-and-stick molecule models, sketched not to scale. Every molecule you add keeps its formula.

Atom count, element by element

Left bars count atoms in the reactants, right bars in the products.

H hydrogenO oxygenC carbonN nitrogen

Coefficients vs subscripts

A coefficient multiplies a whole molecule. A subscript is part of the molecule’s identity. Try both on water:

Coefficient (the big number in front) = how many molecules. You may change it.
Subscript (the small number inside) = which substance. It is locked.