The Atomic Theory
The Atomic Theory
- An element is composed of tiny particles called atoms. All atoms of a given element show the same chemical properties. Atoms of different elements show different properties.
- In an ordinary chemical reaction, atoms move from one substance to another, but no atom of any element disappears or is changed into an atom of another element.
- Compounds are formed when atoms of two or more elements combine. In a given compound, the relative numbers of atoms of each kind are definite and constant. In general, these relative numbers can be expressed as integers or simple fractions.
Law of Conservation of Mass: there is no detectable change in mass in an ordinary chemical reaction
Law of Constant Composition: a compound always contains the same elements in the same proportions by mass
Law of Multiple Proportions: the masses of one element that combine with a fixed mass of the second element are in a ratio of small whole numbers