chemistry scientists Flashcards
first scientist:
Democritus
What did Democritus theorize?
Coined the term “atom.” Thought the atom was indivisible. Supported the particle theory of matter.
Which scientist did not perform any experiments?
Democritus.
Second scientist:
John Dalton
What was Dalton famous for?
Dalton’s atomic theory.
What was Dalton’s atomic theory?
- All matter is made of atoms.
- All atoms of a given element are identical in mass, size, and properties; different atoms have different masses, etc.
3.Atoms cannot be subdivided, created, or destroyed - In chemical reactions, atoms are combined, separated, rearranged.
- Atoms of different elements combine in simple whole number ratios to form compounds.
Which two laws from Dalton’s Atomic Theory are incorrect?
- All atoms of a given elements are identical in mass, size, and properties.
Not true due to the existence of isotopes, which are atoms of the same element with different masses.
- Atoms cannot be subdivided:
Atoms can be divided
Which two scientists did not know that protons, neutrons, and electrons existed?
Democritus and Dalton.
Which two scientists stated that atoms are indivisible?
Democritus and Dalton.
3rd scientist:
J.J. Thomson
What is JJ Thomson famous for?
Discovered electrons. Proved atoms are divisible.
What was Dalton’s model?
The Solid Sphere Model: had no protons, neutrons, or electrons.
What experiment did Thomson perform?
The cathode ray.
Describe the cathode ray experiment
Consisted of a cathode-ray tube and a vacuum pump. When cathode ray, or a beam of electrons, is emitted from the vacuum pump into the tube, the anode side glowed. Cathode rays were deflected by a negatively charged magnetic field.
What model was Thomson’s?
The Plum Pudding Model
Describe the Plum Pudding Model
Just a ball of positive charge with a bunch of electrons scattered around. INCORRECT!
What did Thomson conclude from the Cathode Ray experiment?
Concluded that all cathode rays are composed of electrons, identically negatively charged electrons.
What’s an anode?
A positively charged metal disk
Whats a cathode?
A negatively charged metal disk.
What scientist determined the mass of the electron?
J.J. Thomson
What was the mass of the electron according to Thomson?
-1.76*10^8 C/g
What scientist believed electrons behaved as particles?
JJ Thomson
4th scientist:
Earnest Rutherford
What discovery was rutherford famous for?
Discovered nucleus and protons. Discovered atom was over 99% empty space.
What experiments did rutherford conduct?
The Gold Foil experiment.
Describe the gold foil experiment.
Rutherford bombarded the gold foil with positively charged alpha particles. Checked for wide-angle deflections and ground that 1 in 8000 on the alpha particles deflected back to the source.
What are alpha particles?
Helium Nuclei, positively charged.
What did Rutherford conclude from the gold foil experiment?
That the force causing the deflection was the nucleus, positively charged bundle of matter. Proved proton existed too as it was a positive charge.
5th scientist:
Robert Millikan
What was Millikan famous for?
Mathematically proves electrons exist, and calculated the charge of electrons.
What was the charge of electrons according to Millikan?
1.602*10^-19
What experiment did Millikan conduct?
The oil drop experiment
Describe the oil drop experiment
Sprayed tiny drops of oil into a chamber. Measured how fast the drops fell, then calculated the mass of the individual drops. Sprayed them again but this time he shined x-rays on them, applying an electrical charge. Electrons attached to the oil drops. Found that the drops lined up in a specific way based on the number of electric charges they got. Used the information to calculate the charge of an electron.
6th scientist?
Niels Bohr
What was Bohr famous for?
The discovery of energy levels where electrons move in orbits around the nucleus.
What was Bohr’s model?
The Bohr Model. Had protons inside nucleus, and electrons were in orbits around it.
What was the flaw with Bohr’s model?
Bohr believed the location and speed of electrons can be determined, when they can’t.
Explain Bohr’s findings.
Photon emission. Stated that the electrons can circle the nucleus only in energy levels. Stated that the electron was at its ground level when it was closest to the nucleus and the electron is at its excited state when it’s in a higher-energy level. When the electron falls to a lower level, a photon is emitted. When the electron jumps to a higher level, a photon is absorbed.
7th scientist?
Werner Heisenberg.
What was Heisenberg famous for?
The Heisenberg uncertainty principle.
What was the Heisenberg uncertainty principle.
Stated that you couldn’t know the momentum and location of an electron at once.
What was Heisenberg’s model?
Electron Cloud Model/Quantum Mechanics model.
Explain heissenberg’s model.
Helped visualize the most probable location of electrons in space.
Chronology of the models?
Dalton Model->Plum Pudding Model->Planetary Model->Bohr Model->Electron Cloud Model/Quantum Mechanical Model
