jan 1, 1897 - 1897 J.J. Thomson Tomson stated that an atom is spherical and has a positive charge. Electrons are evenly distributed within the charge. His model of the atom is known as the "plum-pudding" (or chocolate chip cookie) model. This is analogous to a chocolate chip cookie, where the chocolate chips are distributed randomly within the cookie. In this model, the cookie represents the atom, the dough represents the protons and the chocolate chips are the electrons.
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Date:
jan 1, 1897
Now
~ 128 years ago