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100
Acient Greeks create the Continuum Model
Ancient Greek scientists believed that all matter was created of four different particles; water, earth, fire and air. While this statement was incorrect, it was the first theory down a long road of atomic research. -
370
The particle theory
Sometime around 370 BCE, Greek Philosipher Democritus first proposed the theory that all matter was made up of 'tiny, unbreakable particles'. He also was the first to use the word atomos as a term for 'indivisible'. -
The 'Plum Pudding' Model
Joseph John Thompson discovered the electrons and their negtive charge in 1897. He knew that there must also be a positive charge in all matter particles. Several years later he proposed the 'Plum Pudding' model. -
The 'Dynamide' Model is created
In 1904, Philip Lennard theorized that atoms were made up of fast moving 'dynamides', which was a small negative particle attached to a large positive one. -
Rutherford's Experiment
Ernest Rutherford’s experiment was firing a beam of positively charged alpha particles at a piece of gold foil. The fact that some of the particles were deflected began experiments that eventually led to our modern understanding of the nucleus. He eventually created the nuclear model to match his theory. Rutherford’s following experiments led to the discovery of the fact that atoms have a dense nucleus, and the few alpha particles that were deflected off the gold foil were actually reflected off -
The Planetary Model
In 1913, scientist Neils Bohr slightly modified Rutherford's model so that the electrons orbit around the nucleus in set patterns. This model was called the 'Planetary Model' -
The Neutron is discovered
The 3rd main atomic particle was discovered by James Chadwick in 1932. Until this point it was assumed that the nucleus was one posutively charged mass instead of neutrons and protons. Chadwicks discovery shaped how modern scietists view atoms, and a slightly modified version of his model (Which was a Planetary Model but included Neutrons) is still used today.
