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The Evolution of the Atomic Theory


Chadwick discovered a third type of sub-atomic particle which he named the neutron. Neutrons help stabilize the protons in the atom's nucleus. Because the nucleus is so tightly packed together, the positively charged protons tend to repel each other, most times. Neutrons help to reduce the repulsion between protons and stabilize the atom's nucleus.


Below is the model of the atom that Chadwick came up with.


Chadwick's model states that electrons have no definite path in an atom. The most likely location of an electron is found on how much energy it has. The more energy an electron has, the farther from the nucleus. The small, positively charged nucleus is surrounded by a large space in which there are enough negative charged electrons to make the atom neutral.

Chadwick in collaboration with Rutheford realized that the atomic mass of most elements was about double the number of protons

Chemirty 11 project The Evolution of the Atomic Theory