Dalton's theory explained that all matter constitutes of atoms that are indivisible and indestructible. They combine in definite ratios and posses definite masses. He considered atom to be the smallest particles that the matter is composed of. He basically explained about the chemical properties of matter.
After many more researches, it was explained that atom is not the smallest particle that the matter is composed of but it contains many subatomic particles like protons, neutrons and electrons that the matter is made of. Dalton could not explain about the nuclear property of atom.
