AI Tutor
If you take a block of pure gold and keep slicing it in half over and over, can you slice it forever, or will you eventually hit an uncuttable piece?
In 1803, an English schoolteacher named John Dalton proposed that matter reaches a definitive stopping point: tiny, solid, indivisible spheres called atoms.
Dalton didn't just guess — he synthesized two proven chemical laws to build the first scientific model of the atom.
What specific claims did Dalton make, and how did he picture these fundamental particles interacting?

Dalton's Five Postulates

Dalton laid out his model as five core postulates — fundamental assumptions accepted as true to build a scientific theory.
  1. All matter is composed of extremely small, indivisible particles called atoms.
  2. All atoms of a given element are identical in mass and properties.
  3. Atoms of different elements possess different masses and properties.
  4. Compounds are formed when atoms of different elements combine in simple, whole-number ratios.
  5. In chemical reactions, atoms are combined, separated, or rearranged, but never created, destroyed, or transformed into atoms of another element.
Let's see how Dalton's fourth postulate directly explains the Law of Multiple Proportions with a concrete calculation.

Worked Example: Combining Ratios

Carbon and oxygen can react to form two distinct gases: Carbon Monoxide (CO\text{CO}) and Carbon Dioxide (CO2\text{CO}_2).
In CO\text{CO}, exactly 12 g12\text{ g} of carbon reacts with 16 g16\text{ g} of oxygen. In CO2\text{CO}_2, 12 g12\text{ g} of carbon reacts with 32 g32\text{ g} of oxygen.