How were atomic models developed when no one had seen an atom?

How does a hydroelectric power plant converts energy into energy.

The minerals found in bones are deposited by living cells called

Skills of homo sapiens were found an excavation. the skulls were preserved because the bodies were frozen. so, these fossils are (blank) fossils.the image shows the evolution of skulls beginning 2 to 3 million years ago. based on the image, modern human skulls(blank) ape skulls.