Word and Symbol Equations

Chemical equations are like recipes. They show the starting substances (reactants) and what they make (products). We can write them in words or using chemical symbols and formulas.

Word equations

A word equation names each substance. Plus signs separate substances, and an arrow shows what is produced.

Example: magnesium + oxygen → magnesium oxide

Symbol equations

A symbol equation uses formulas and can include state symbols: (s) solid, (l) liquid, (g) gas, (aq) dissolved in water. Equations must be balanced to obey conservation of mass: the number of each type of atom is the same on both sides.

• Count atoms on both sides.
• Change only big numbers in front (coefficients), never the small numbers in formulas (subscripts).
• Keep polyatomic ions together if they appear unchanged on both sides (helps balancing).

Common diatomic elements (they exist as two-atom molecules): H2, N2, O2, F2, Cl2, Br2, I2.

Key points

• Word equations describe reactions in names; symbol equations use formulas and must be balanced.
• Coefficients show the ratio of particles reacting.
• State symbols give physical states and make equations clearer.