Origins Of Quantum Theory Flashcards
How did Democritus contributed?
Theorized that matter is made up of elementary particles called atoms
How did John Dalton contributed?
Stated
- elements consist of atoms
- atoms cannot be created, destroyed or divided
- atoms of the same element have identical size, mass, and other properties
Ideas led to Law of Conservation of Mass and Law of Constant Composition
How did J.J Thomson contributed?
- provided evidence for the existence of the electron
- theorized atoms consist of positively charged clouds with negatively charged electrons embedded in it
How did Robert Millikan contributed?
- able to determine mass of electron
- mass was 9.11 x 10-31 kg
How did Ernest Rutherford contributed?
- Figured out atom has dense positivity charged centre (nucleus), surrounded by empty space
- gave the positive particles the name protons
- propose theory of radioactivity
How did Chadwick contributed?
- discovered neutrons in the nucleus
How did Heinrich Hertz contributed?
- discovered the photoelectric effect
- found light shining on a metal surface causes the emissions of electrons from the metal (light bounced off)
How did Plank contributed?
- showed that energy could be lost or gained in quanta or small amounts of energy, according to the equation: E=nhf
- light was emitted in bursts in quantity of energy instead of a stream
How did Einstein contributed?
- explained photoelectric effect
- explained how electromagnetic radiation could be viewed as a stream of particles called photons, units of light energy
- creates the quantum theory
What is radioactivity?
Spontaneous decay of the nucleus
What makes certain atoms of certain elements radioactive?
The answer is found in the isotopes of some elements (because they have more protons than neutrons
When the nuclei of isotopes are unstable, they are radioactive
