The postulate of Dalton’s atomic theory that explains the law of definite proportions is: “Atoms of different elements combine in simple whole number ratios to form compounds.” This postulate is based on the idea that atoms combine in a fixed ratio, meaning that the proportion of each element in a compound is constant.
Explanation:
Law of Definite Proportions:
This law states that a chemical compound always contains the same elements in the same proportion by mass.
Dalton’s Postulate:
By stating that atoms combine in simple whole number ratios, Dalton’s theory explains why the ratio of elements in a compound is always the same. For example, water (H₂O) always contains two hydrogen atoms for every one oxygen atom, regardless of the source or how it’s made.
Constant Proportion:
This fixed ratio of atoms results in a constant proportion of elements by mass within the compound.
In simpler terms: Imagine building a house with LEGO bricks. If you always use the same number of each type of brick, you’ll always have the same ratio of different brick types in the final house, just like the proportions of elements in a compound are always the same.