1 A few types of cells are large enough to be seen by the unaided eye. The human egg (ovum) is the largest cell in the body, and can (just) be seen without the aid of a microscope. 2  Most cells are small for two main reasons:  The cellâs nucleus can only control a certain volume of active cytoplasm.
The atomic nucleus is the small, dense region consisting of protons and neutrons at the center of an atom, discovered in 1911 by Ernest Rutherford based on the 1909 GeigerâMarsden gold foil experiment.
Who are the scientists who contributed to the development of the model of the atom? J.J. Thomson, chemist, discovered the negative particle (electron) in the atom. Goldstein, scientist, discovered the positively charged particle (electron) in the atom.