The combination of different elements to form compounds is governed by certain basic rules. These rules are referred to as laws of chemical combination. There are five basic laws of chemical combination that govern the chemical combinations of elements:
Law of Conservation of Mass
It states that matter is neither created nor destroyed during a chemical reaction, though it may change from one form to another. Total mass of products is equal to total mass of reactants. It was given by Antoine Lavoisier in the year 1789 based on the data he obtained after carefully studying numerous combustion reactions. The balancing of chemical equation follows the law of conservation of mass. The law does not hold good for nuclear reactions.
Law of Constant Proportion
A chemical compound always contains the same elements combined together in the fixed ratio of their masses whatever be its method of preparation. This observation was first made by the French chemist Joseph Proust, based on several experiments conducted between 1798 and 1804.note This law does not hold good for non-stoichiometric compound. For example, Wusitite Fe0.95O. It was given Proust.
Law of Multiple Proportion
When two elements A and B combine to form more than one chemical compounds then different weights of A, which combine with fixed weights of B, are in a simple whole number ratio. It is sometimes called Dalton's Law after its discoverer, the British chemist, John Dalton.
Law of Reciprocal Proportion
When two elements combine separately with a fixed mass of third element then the ratio in which they do so is either the same or whole number multiple of the ratio in which they combine with each other. The law of reciprocal proportions was proposed in essence by Richter, following his determination of neutralisation ratios of metals with acids.
Gay Lussac's Law
At a given temperature and pressure when gases combine, they do so in volumes, which bear a simple ratio to each other and also to the gaseous product formed.