Final answer:
The existence of atoms is supported by evidence from historical atomic theory, experimental discovery of the electron, and the observation and explanation of Brownian motion.
Step-by-step explanation:
Evidence for the Existence of Atoms
Atoms are the fundamental building blocks of matter, and their existence has been proven through various lines of evidence. Three different types of evidence for the existence of atoms include:
- Atomic Theory: John Dalton's atomic theory proposed that all matter is composed of atoms, which are indivisible and indestructible particles. This theory explained why elements always react in ratios of whole numbers (the law of multiple proportions).
- Discovery of Electron: Experiments by J.J. Thomson showed that cathode rays were streams of negatively charged particles, which he called electrons. This discovery revealed that atoms are divisible and contain smaller, subatomic particles.
- Brownian Motion: First observed by Robert Brown, this is the random movement of particles suspended in a fluid (liquid or gas) resulting from their collision with the quick atoms or molecules in the gas or liquid. Albert Einstein's mathematical explanation of this phenomenon provided further evidence for the existence of atoms.
These pieces of evidence collectively substantiate the atomic theory and the existence of atoms as the basic unit of matter.