Structure of an Atom

Events

Democritus

Approx. 400 BC

Came up with the first idea of an atom. These atoms, he believed, were eternal and invisible; absolutely small, so small that their size cannot be destroyed. They absolutely full and incompressible, as they are without pores and entirely fill the space they occupy; and homogeneous, differing only in shape, arrangement, position, and magnitude.

John Dalton

1766 - 1844

Created the modern idea of atoms (the Atomic Theory). All atoms are the same but some properties were slightly different.
-All atoms of a given element are identical.
-The atoms of different elements vary in mass and size.
-Atoms are indestructible. Chemical reactions may result in their rearrangement, but not their creation or destruction.

Joseph John Tomson

1856 - 1940

Credited with the discovery of the Electron. He demonstrated that cathode rays were negatively charged. In addition, he also studied positively charged particles in neon gas. He created a model of the atom with plum pudding. The negative electrons represented the raisins in the pudding and the dough contained the positive charge.
-He did this using a cathode ray tube, which is a vacuum-sealed tube with a cathode and anode on one end that creates a beam of electrons travelling towards the other end of the tube.

Ernest Rutherford

1871 - 1937

He was the first to split an atom.
-Gold Foil Experiment.

- According to him practically the whole mass of the atom and at the same time all positive charge of the atom is concentrated in a minute space at the center.

Niels Bohr

1885 - 1962

Was able to create the pictures of a Nucleus, and the electrons in an atom
But was completely wrong
-he proposed that energy levels of electrons are discrete and that the electrons revolve in stable orbits around the atomic nucleus but can jump from one energy level to another.
-Bohr Model

Schrodinger

1887 - 1961

How electrons move around atoms
-Electron Cloud Model
-Schrödinger used mathematical equations to describe the likelihood of finding an electron in a certain position. This atomic model is known as the quantum mechanical model of the atom.
-He figured out there is no direct path of an atom or electron

James Chadwick

1891 - 1974

Chadwick bombarded beryllium atoms with new particles. And an unknown radiation was produced. Chadwick figured out this radiation was being composed of particles with a neutral electrical charge and the approximate mass of a proton. This particle became known as the neutron.

De Broglie

1892 - 1987

French Physicist who developed a revolutionary theory of electron waves. De Broglie’s idea of an electron with the properties of a wave offered an explanation of the restricted motion.

Heisenburg

1901 - 1976

Came up with the uncertainty

Joseph Rotblat

1908 - 2005

-He was one of the main scientists when they made the atomic bomb
- He was still in school when they split the first atom.
-He saw that atomic bombs were only the first step on a terrible path. People would look for more powerful bombs - the idea of the hydrogen bomb had already been conceived; made people extremely interested in what else they could create.