https://padlet.com/203807/xyoe33o1u3d Made with charisma en-us 2016-11-10 18:14:19 UTC 2026-02-25 08:06:19 UTC hello@padlet.com 203678 https://padlet.com/203807/xyoe33o1u3d/wish/136837229 Democritus was a Greek philosopher that discovered atoms in 400 BC. He thought atoms were small hard particles that were different shapes and sizes. Aristotle did not believe Democritus. He thought that all substances are made up of fire, water, air, and earth.
 Democritus - (notes)
Aristotle - (Link)


]]> 2016-11-10 18:23:40 UTC https://padlet.com/203807/xyoe33o1u3d/wish/136837229 203807 https://padlet.com/203807/xyoe33o1u3d/wish/136838756 John Dalton created a theory in the 1800's that supported Democritus' theory that all things are made of atoms. He believed that the atom was an indivisible hard ball, and that the atoms of the same element are exactly alike. (notes) (pic)]]> 2016-11-10 18:26:50 UTC https://padlet.com/203807/xyoe33o1u3d/wish/136838756 203678 https://padlet.com/203807/xyoe33o1u3d/wish/136839787 He discovered electrons and also discovered that atoms can be split. This led him to develop the Plum Pudding Model. The model shows that electrons are surrounding negative and positive charges. This was the best model of an atom before the nucleus was discovered.
(link)]]> 2016-11-10 18:29:05 UTC https://padlet.com/203807/xyoe33o1u3d/wish/136839787 203807 https://padlet.com/203807/xyoe33o1u3d/wish/136841115 Ernest Rutherford discovered the nucleus in 1908 when he shot alpha particles through a thin sheet of gold, and the bullets went in different directions, and sometimes bounced back. He realized that a positive charge must be causing the alpha particles to repel, so he said that there is a nucleus with a positive charge in the center of the atom. (notes) (Video) (pic)]]> 2016-11-10 18:32:22 UTC https://padlet.com/203807/xyoe33o1u3d/wish/136841115 203807 https://padlet.com/203807/xyoe33o1u3d/wish/136841840 In the 1900's, scientists debated whether electrons move in waves or they are particles. Scientists eventually compromised that electrons are both. They are particles that move in waves. This is called the Quantum Mechanical Theory. They observed that the nucleus is tiny, and that electrons form a cloud that has a lot of empty space in it. (notes) (pic)]]> 2016-11-10 18:34:06 UTC https://padlet.com/203807/xyoe33o1u3d/wish/136841840 203678 https://padlet.com/203807/xyoe33o1u3d/wish/136842271 He discovered a orbit model of an atom. Electrons can only have certain energy levels.
(link) ]]> 2016-11-10 18:35:16 UTC https://padlet.com/203807/xyoe33o1u3d/wish/136842271 203678 https://padlet.com/203807/xyoe33o1u3d/wish/137064872 Discovered the Neutron
(link)]]> 2016-11-11 18:00:31 UTC https://padlet.com/203807/xyoe33o1u3d/wish/137064872 203807 https://padlet.com/203807/xyoe33o1u3d/wish/137065478 In 1913, Henry Moseley experimented wavelengths of X-rays and discovered that the same elements have the same number of protons, which is their atomic number. Also, different elements have a different number of protons/atomic number. (Link) (pic)]]> 2016-11-11 18:03:25 UTC https://padlet.com/203807/xyoe33o1u3d/wish/137065478 203678 https://padlet.com/203807/xyoe33o1u3d/wish/137065808 They discovered two radioactive elements, polonium and radium. 
(link)]]> 2016-11-11 18:05:06 UTC https://padlet.com/203807/xyoe33o1u3d/wish/137065808