Nucleolus+(plum+pudding)

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** Development of the Atom **

The term __atom__ comes from the Greek word “atomos” meaning indivisible. __Democritus__, a Greek Philosopher, believed that all matter was made up of tiny indivisible particles.

2000 years later, __John Dalton__ gave shape to these tiny particles. He envisioned them as round balls, uniform throughout.

As scientific equipment became more advanced, scientists uncovered a more complex atom.

__ J.J. Thomson __ used the cathode ray tube to discover a negatively charged particle within the atom which he called the electron. Based on his research, he developed the "plum-pudding” model of the atom. In this model, electrons were imbedded randomly throughout the atom.

__Ernest Rutherford__ used his “gold foil experiment” to find the positively charged nucleus. During the experiment, he shot alpha particles at gold foil expecting their path to be only slightly altered. However to his amazement, most of the alpha particles went straight through the foil, some scattered at small angles, and a few deflected at large angles. As a result of his findings, he concluded that there was a tiny, dense, positive center at the middle of the atom which he called the nucleus with electrons moving randomly in the vast space around it. Rutherford called the positive charge in the nucleus a proton.

__ James Chadwick __ focused his research on the nucleus. Evidence told him that there was more than just the proton in the nucleus. To find this particle, he bombarded Beryllium with alpha particles from Polonium and in the process discovered a neutral particle in the nucleus.