In simple terms, that assertion is correct, but for those with an expertise in the field, the longer answer to who did it ...

Up to two electrons may exist in the atom's first shell. Up to eight electrons may exist in the atom's second shell. An electron may "drop" from an outer shell if an inner shell is not full.

J.J. Thomson — a professor of experimental physics at the University of Cambridge, who in 1897 discovered the electron and in 1904 proposed a model of the atom — was the first person to be ...

BBC Bitesize A simple model of an atom shows a nucleus orbited ... which have been described as being the first to "split the atom". He blasted beams of radioactive particles into nitrogen gas ...