Development of Atomic theory

:(

changes

always changing with new technology

atomos

• matter cannot be constantly divided 

• tiny, invisible, indestructible 

• created by Democritus 

• 400 B.C. 

• Created by philosophy  

Earth, Air, Fire, Water

• matter can constantly be cut 

• four fundamental elements with basic qualities 

• created by Aristotle 

• 350 B.C. 

• Created by philosophy 

solid sphere model

• five concepts to the theory 

• discovered through testing gasses 

• created by John Dalton 

• Created through scientific discovery (testing gasses) 

• 1803 

five concepts to solid sphere model

• all elements are made of invisible particles that cannot be broken down further

• atoms of a given element are similar in chemical and physical properties

• atoms of different elements differ in their physical and chemical properties

• atoms of different elements combine in simple, whole number ratios to make compounds

• in chemical reactions, atoms are combined, separated, or rearranged, but never created, destroyed, or changed

Plum pudding model

• an atom is a positive charged cloud with electrons scattered inside 

• discovered that there must be positive charge around the electrons to balance out their negative charge 

• discovered by the cathode ray tube 

• created by JJ Thomson 

• 1904 

cathode ray tube

• discovered that atoms can be further broken down

• discovered negatively charged particles

• electrons move towards the anode (positive electrode) because opposites attract, and away from the cathode (negative electrode) because similar repel

nuclear model

• some alpha particles bounced off a proton and some passed through

  • the ones that deflected proved protons are denser and there is a positive charge in the core

  • the ones that passed through proves electrons are less dense and cover empty space while still orbiting the nucleus

• Created by Ernest Rutherford

• 1911

planetary model/Bohr model

• similar to planets (electrons) orbiting the sun (proton) 

• rings are called energy levels/orbitals 

• orbit at different distances 

• electron moving down gives off/releases energy 

• electrons moving up use/absorb energy 

• strict number of electrons per orbital 

• 1913 

Quantum model

• predicts the probability of finding electrons location/paths in an electron cloud

• electrons viewed as particle/wave

• cloud of probability

  • it is an electron cloud moving as a particle/wave

  • most likely to find electrons

• 1926