In the previous Chapter, we looked at atom as the most fundamental unit. We said that it was not made up of anything else. But, in reality, scientists discovered that atoms are not the most fundamental units of matter.

Atoms themselves are made up of other particles, called subatomic particles. The Hydrogen atom is different from the Oxygen atom because both of them contain different numbers of subatomic particles.
Which of Dalton's hypotheses (statements) about the atom contradicts atoms having subatomic particles?
  • Atoms of a given element are identical in mass and chemical properties
  • Atoms are indivisible particles
  • Atoms combine in the ratio of small whole numbers to form compounds
  • Atoms of different elements have different masses and chemical properties