In a chemical reaction, the total number of atoms before and after the reaction remains the same. This observation is known as the law of conservation of mass or the law of conservation of atoms.
According to this fundamental principle, atoms are neither created nor destroyed during a chemical reaction. This means that the total number of atoms of each element present in the reactants must be equal to the total number of atoms of each element in the products.
For example, let's consider the reaction between hydrogen gas (H₂) and oxygen gas (O₂) to form water (H₂O):
2H₂ + O₂ → 2H₂O
In this reaction, there are four hydrogen atoms and two oxygen atoms on the left side (reactants), and after the reaction, there are still four hydrogen atoms and two oxygen atoms on the right side (products). The number of atoms of each element remains conserved.
This principle holds true for all chemical reactions, regardless of the complexity of the reaction or the number of elements involved. It is a fundamental concept in chemistry and provides the basis for balancing chemical equations.