[CH 21.2] Atomic Physics: Models of The Atom Flashcards
How was the model of the atom Newton’s days?
It was a model that represented a a tiny, hard, and indestructible sphere.
What is the kinetic theory?
It proposes that all matter is composed of tiny particles (atoms or molecules) that are constantly in motion.
The model in Newton’s days was a good basis for…
the kinetic theory.
When was the electron discovered, and by who?
It was discovered by J.J. Thomson in 1897 (to suggest a new model of atom; the plum pudding/watermelon model).
What did J.J. Thomsom’s model propose about the structure of the atom?
It proposed that it was a spherical volume of positive charges, in which electrons are embedded, like a watermelon.
What did Ernest Rutherford propose, with the help of Hans Geiger and Ernest Marsden perform?
They perdormed an experiment to show that Thomson’s model was not entirely correct.
What did the experiment that Ernest Rutherford, Hans Geiger and Ernest Marsden perform?
A beam of positively charged alpha particles (that resemble helium atoms) was beamed against a thin metal foil.
What were the results of the foil experiment, and what does it prove?
Most of the alpha particles passed through the foil as if it were empty space, and some alpha particles were deflected from their original direction through very large angles (and some where even deflected bckwards).
This proves that the positive charge is not evenly distrubuted throughout the atom. Thomsom then proposed that the positive charge only made up a small part of the atom in the center, and that the electrons revolved around that center.
What’s wrong with Rutherford’s model?
The electrons are orbiting the nucleus, suggesting that they would have to undergo centripetal acceleration, which would mean they are unstable (and would collapse).
What does Maxwell’s theory of magnetism state?
Accelerated charges eventually lose energy.
