Final answer:
The structured patterns of the periodic table provide indirect evidence for atoms, while Brownian motion provides direct evidence by visualizing the effects of atom-sized particles on visible matter. Atoms are too small to be seen with visible light, being smaller than its wavelength.
Step-by-step explanation:
The patterns in the periodic table of the elements provide evidence for the existence of atoms because these patterns result from the properties of atoms as they increase in atomic number, indicating a structured arrangement based on atomic characteristics.
Conversely, Brownian motion offers a more direct observation of atomic existence. Scientist Robert Brown discovered that particles in fluid move erratically, not due to currents, but because of countless collisions with smaller, invisible particles—atoms or molecules. By analyzing these movements, the size and presence of atoms can be inferred.
Atoms cannot be seen with visible light because their size is much smaller than the wavelength of visible light, which typically ranges from about 390 to 700 nanometers. The average size of an atom is approximately 100 picometers (10-10 meters), which makes them too small to be detected by the human eye or even with most optical microscopes.