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442 BCE
Democritus' model
His atomic model was solid and stated all atoms differ in size, shape, mass, position, and arrangement, with a void, exists between them. He called these infinitesimally small pieces of matter atomos, meaning "indivisible." He suggested that atomos were eternal and could not be destroyed. (Weebly, n.d.)
Main contribution to current understanding: First to identify the atom and said that they can´t be divided.
What's wrong?: It's vage, it doesn't represent anything else than an atom. -
Billiard Ball Model / Solid Sphere Model - Dalton
Atomic theory: 1. Matter consists of indivisible atoms.
2. All of the atoms of a given chemical element are identical in mass and in all other properties.
3. Different chemical elements have different kinds of atoms; in particular, their atoms have different masses. etc. (Weebly, n.d.)
Main contribution: The atomic theory
What's wrong?: The indivisibility -
Plum Pudding Model - Thomson
As each atom was a sphere filled with a positively charged fluid, known as the “pudding”. Scattered in this fluid were negatively charged electrons, these were the “plums”. The discovery of the electron (Weebly, n.d.)
Main contribution: The electron
What's wrong?: The positive charge is scattered, just like the electrons. -
Planetary Model - Rutherford
He named this center the nucleus. He then said that negatively charged electrons were scattered surrounding this dense, positively charged center. He stated these negatively charged electrons were held in orbit by the positively charged nucleus, due to the electrical forces. He performed with alpha particles. (Weebly, n.d.)
Main contribution: The discovery of the nucleus and that the electrons orbit around the nucleus.
What's Wrong?: That the electrons are just scattered. -
Energy Level Model - Bohr
He stated the electrons moved in fixed, circular orbits around the nucleus, electron shells. These shells were at set distances from the nucleus and were the same for all atoms. They become larger the further away they are from the nucleus, and that electrons furthest from the nucleus have higher energy. (Weebly, n.d.)
Main contribution: Shells - N.M, L K. Electrons jumps from one orbital to another.
What's wrong?: It doesn't account the sublevels nor the neutron. -
Quantum Mechanical Model - Schrödinger
Schrodinger discovered that electrons don't move in orbits (or in a set path at all). He theorizes electrons move in waves, and they have no exact location.
Main contribution: Schrödinger used mathematical equations to describe the likelihood of finding an electron in a certain position. It doesn't define an exact path for the electron. (Weebly, n.d.)
What's Wrong?: It doesn't define the neutron.
