History Flashcards
Where and when did the idea of the atom originate? By who?
Ancient Greece (400 B.C.)
Democritus and Leucippus (Greek philosophers)
What is the modern model of the atom called?
The BOHR model
What was the (incorrect) theory that Aristotle and Plato favored?
Earth, air, fire, and water approach to the nature of matter
What was Dalton’s atomic theory? (3 sentences)
- All matter is made of invisible particles called atoms.
- Atoms of the same element are identical, those of different elements are different.
- Atoms of different elements combine in whole number ratios to form compounds.
What was Dalton’s model (#1) of the atom?
Billard Ball Model
What did Crookes discover/invent?
Cathode Ray Tube
What did Sir JJ Thomson discover? Using what? And what model did he use?
Electrons, Cathode Ray Tube, Plum Pudding Model
What are the characteristics of Thomson (#2) model of the atom?
The atom is a solid, positively charged sphere with negative electrons scattered throughout.
What are the pros of Thomson’s model of the atom?
- Introduces the idea of charged particles within the atom
- Discovers the electron (1st subatomic particle)
What are the cons of Thomson’s model of the atom?
- Atom solid sphere
- Doesn’t explain future experiments
What did Millikan and Rutherford determine?
Mass and charge of an electron (9.1 x 10^-28)
What was Rutherford’s experiment? What are the characteristics?
The Gold Foil Experiment
Used a zinc sulfide coated screen to detect radioactive alpha particles
What was the outcome of Rutherford’s experiment?
Alpha particles bounced back at him
What does Rutherford Model (#3) of the atom look like?
Atom is mostly empty, small dense positive nucleus in the center, electrons scattered around the nucleus
What did Niels Bohr propose?
He proposed a new improvement to the atomic model where electrons have definite energy levels around the nucleus. (#4 Planetary Model)
What is a quanta of energy?
The amount of energy needed to move an electron from one energy level to another.
What is a photon?
The minimum energy to release an electron out of an atom.
(Light particles)
What did Moseley discover?
Protons
What did Chadwick discover?
Neutrons
What did Heisenberg discover? Describe it?
The Uncertainty Principle
- The more precisely the position of an electron is determined, the less precisely the momentum is known in that instant (and vice versa)
What did Schrodinger create?
The current model of the atom
(#5) Charge-Cloud Model or Quantum Mechanical Model
What is an orbital?
3D mathematical probability regions where an electron can live
What are the Keeps?
The concept of energies being quantized in certain energy levels
What are the Discards?
2D concept of orbits discarded in favor of orbitals
What does a S-Orbital diagram look like?
Spherical
What does a P-Orbital diagram look like?
Dumbell
