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442 BCE
Democritus
-Atomic model: stated that matter consists of invisible particles called atoms and a void empty space.He stated that atoms are indestructible and unchangeable. His atomic model was solid, and stated all atoms differ in size, shape, mass. -
John Dalton
Billard Ball Model
+Atoms are solid spheres
+Indivisible
+Indestructible
+Smallest particle that retains the properties of an element
+Dalton´s atomic theory formed the basis of current atomic theory, although we have some modifications
+We know that atoms are nos completely solid spheres and that its structure is composed by different parts and types of atoms.
+All atoms of a given element are the same and different from other elements
+Atoms are neither created nor destroyed in a chem reaction -
Thomson
-Atomic model: ¨Plum pudding model¨. The atom is composed of electrons surrounded by a soup of positive charge to balance the e- negative charges, like negatively charged “plums” surrounded by positively charged “pudding”. He used the cathode ray experiment and also discovered the electron. His model was ¨wrong¨ because he assumed that the electrons were uniformly distributed and free to rotate in rings inside a sphere of positive charge. -
Ernest Rutherford
Rutherford atomic model, also called nuclear atom or planetary model of the atom, description of the structure of atoms proposed (1911) by the New Zealand-born physicist Ernest Rutherford. The model described the atom as a tiny, dense, positively charged core called a nucleus, in which nearly all the mass is concentrated, around which the light, negative constituents, called electrons, circulate at some distance, much like planets revolving around the Sun. -
Niels Bohr
Bohr´s atomic mdel: Also called "solar system model". -CHARACTERISTICS:
+Atoms have only certain allowable energy states.
+Electrons moved around the nucleus in only certain allowed circular orbits.
+Bohr assigned a number, n, called a quantum number to each orbit or energy level.
+The smaller the orbit, the lower the atom´s energy. The error was that it breaks down when applied to multi-electron atoms. It does not account for sublevels (s,p,d,f), orbitals or elecrtron spin. -
Erwin Schrödinger
"Electron Cloud or Quantum Mechanics Models" -Levels are divided into sublevels and sublevels are divided into orbitals.
-We cannot know the exact location of an electron.
-The atom only just respect the quantum laws.
-Uses complex formulas to measure.
