# Chemical Formulae and Equations

Chemical Formulae and Equations

Basic Information

• A chemical formula is a way of presenting information about the proportional amounts of atoms that constitute a particular chemical compound.
• A chemical equation shows the reactants and products in a chemical reaction.

Writing Chemical Formulae

• Each different element in a compound is represented by its chemical symbol from the Periodic Table.
• A subscript number after an element symbol shows how many atoms of that element are present in each molecule of the compound. If there’s no subscript number, it implies one atom is present.
• Ionic compounds are formed by the transfer of electrons from a metal to a non-metal. The chemical formula represents the minimum numbers of ions required for electrical neutrality.
• Molecular compounds (also called covalent compounds) are formed by sharing electrons. The chemical formula represents the actual numbers of each type of atom in each molecule.

Balancing Chemical Equations

• Chemical equations must be balanced to satisfy the law of conservation of mass, which states that atoms are not lost or gained in a chemical reaction.
• To balance a chemical equation, adjust the number of each type of atom on both sides of the equation so they match.
• Round bottom numbers can be added before the compound to balance the quantity.

State Symbols in Chemical Equations

• State symbols show the physical state of each substance in an equation at room temperature.
• `(s)` represents a solid, `(l)` is for a liquid, `(g)` indicates a gas, and `(aq)` stands for an aqueous solution (dissolved in water).

Key Aspects to Remember

• The reactants are the substances present before a reaction takes place, and they’re written on the left-hand side of an equation.
• The products are the new substances formed during a reaction, and they’re written on the right-hand side.
• An arrow `-->` separates the reactants from the products and shows the direction of the reaction.

Keywords to Remember

• Chemical Formula: A representation of a substance using symbols for its constituent elements.
• Chemical Equation: A written symbolical representation of a chemical reaction.
• Reactants: Starting materials in a chemical reaction.
• Products: The ending materials in a chemical reaction.

Knowing how to read and balance chemical equations is fundamental to understanding chemical reactions and the conservation of mass principle. This will also help in predicting the result of a reaction. Keep practising writing and balancing equations to gain proficiency.