Reading and understanding
Count every atom deliberately
When learning to balance equations, write the same chemical elements down the side of a table and use one column for reactants and another for products. Multiply each atom count in a substance by that substance's coefficient. If an element appears in several substances on one side, add the totals. A chemical equation is balanced only when all of the element rows match. Checking just oxygen while ignoring hydrogen is not sufficient.
Do not change the species
Try Fe + O₂ → Fe₂O₃. Iron atoms are counted individually on the left, while the product contains two iron atoms per formula unit. Oxygen is found in pairs on the left and groups of three on the right. A useful shared oxygen count is six, which means three O₂ and two Fe₂O₃. That provides four iron atoms on the right, so place four Fe on the left. Final: 4Fe + 3O₂ → 2Fe₂O₃.
Make coefficients minimal
Sometimes all element totals match, but the coefficients share a common factor. For instance, 4H₂ + 2O₂ → 4H₂O balances atoms, yet can be simplified to 2H₂ + O₂ → 2H₂O by dividing every coefficient by two. We usually report the smallest positive whole-number coefficients. The multiplier applies to each full formula; subscripts cannot be changed to achieve a smaller solution.
Separate ratios from masses
Coefficients tell us ratios among amounts of chemical entities, not grams of material by themselves. To calculate masses you need information about molar masses, which the next week covers. A balanced equation is a model of atom conservation; it says nothing on its own about the reaction's speed or its practical safety. The offline arena helps practice ten or more structural examples without performing those reactions.