Story Of Atom Flashcards
What do GOOD theories have in common?
Based on observations and reasonable inferences
Change as new evidence is discovered
Democritus
Atoms were invisible particles
John Dalton
Atoms are invisible solids, like marbles. They are smallest possible particle of matter
No evidence supporting his theory
JJ Tomson
Discovered electrons and thought they’re small negatively charged particles. They are building blocks of atoms
Tomson’s Model
Atoms NOT smallest particle and NOT solid. Plum Pudding Model: electrons are studded like chocolate in cookie
Eugene Goldstein
Discover positively charged protons after Tomson’s Model was accepted. Mass of 1 (1840 times electrons)
James Chadwick
Confirmed existence of “neutron”. Particle with no change but mass like protons
Charge of electron
-1
Charge of protons
1
Charge of neutron
0
Rutherford’s experiment
Shot aloha particles at gold foil
If Tomson & Dalton were correct, all particles should pass straight through OR all particles would bounce off. Result: some passed through and some bounced off
Interpretation of Rutherford’s experiment
Atoms are not solid, it must be made of empty space
Alpha particles must have gotten close to smth with positive charged because deflected at angle
Rutherford’s Model
Atom is mostly empty space with dense positively charged nucleus at center and electrons around outside
Couldn’t explain why electron wouldn’t collapse into Nucleus
Bohr Model
Atom is mostly empty space with dense positively charged nucleus at center and electrons around outside.
Electrons orbit nucleus like planets orbit sun
J. J. Balmer
Studied line spectra given off by hydrogen atom. Came up with equation that fit wavelengths of lines perrectly
Bohr with Balmer’s equation
Electron fell from higher to lower orbit must release energy. Distance between Bohr’s orbits matched light given from hydrogen atom
Problem: electrons would have to travel faster than speed of light
Quantum Mechanics
Resulted from Bohr’s model.
Based on portability and where electrons are approximately located at
Schrodinger response to Quantum mechanics
If you know energy of electron, you CAN’T know where it exact position
Heisenberg Uncertainty Principle
Idea of orbitals that show where electron is 90% of the time
Quantum Mechanics model
Electrons generally travel around nucleus in orbits. Area of probability where electrons are 90% of the time makes up the picture of electron cloud
Flaws about Rutherford’s Experiment
Do not explain why there were so few alpha particles deflected.
