History Of Atoms Flashcards
Who investigated why gases glow?
William Crookes
Who first suggested the existence of tiny fundamental particles that make up matter?
Democritus of Abdera
What is Dalton’s Atomic Theory?
- All elements are composed of tiny individual particles -
called atoms. - All matter is composed of combinations of these atoms.
- Atoms of different elements are different.
- Atoms of the same element have the same size, mass, and form.
What was JJ Thomson’s experiment?
- he continued Crookes work.
- applied an electric field which bent the light inside the tube back to a straight path and was able to measure this field.
What was William Crookes?
A British Physicist.
What were the outcomes of JJ Thomson’s experiment?
- discovered the electron.
- used the strength of the field and was able to determine the charge-to-mass ratio of this negative particle beam.
- determined the existence of the proton (because of neutrality).
What was JJ Thomson?
A British Physicist.
What were the outcomes of Crookes’ experiment?
- determined that particles have a negative charge.
- created the cathode ray tube (also known as Crookes tube).
What were the pros and cons of Dalton?
Pro: advance in the description and nature of chemical reactions.
Con: did not hold up when subatomic particles were discovered.
Where was Democritus of Abdera from?
Ancient Greece.
What did the plum pudding model show?
Negatively charged electrons embedded in a positive mass of proton”ness”.
Where was John Dalton from?
Eaglesfield, England.
What were JJ Thomson’s pros and cons?
Pro: did explain some of the electrical nature of matter.
Con: did not say anything about the number of charged particles or their arrangement.
Which scientist created the Plum Pudding Model?
JJ Thomson
Who was a U.S. Physicist?
Robert Millikan
What was Millikan’s experiment?
The oil drop experiment.
What were the outcomes to Millikan’s experiment?
- determined the charge on a single electron.
- using the charge-to-mass ratio from Thomson, many scientists determined the mass of an electron.
Who discovered x-rays?
William Roentgen
What is the difference between x-rays and electrons?
X-rays are energy while electrons are matter.
What was Henri Becquerel?
A French scientist.
What was Henri Becquerel’s situation?
He left a sample of uranium ore in a drawer with glass photo plates and there was fogging on the plate.
What is a discovery on accident?
A serendipity.
What were Becquerel’s outcomes?
- concluded something itself must be capable of “fogging” the plates; the sample must give off some kind of ray without the influence of the sun.
- rays were a product of radioactivity.
Who were Marie and Pierre Curie?
French Physicists who studied radioactivity.
What did Marie discover?
Polonium, which she named after Poland.
Who conducted the Gold Foil Experiment?
Ernest Rutherford
What did Ernest Rutherford do?
- discovered the nucleus of the atom.
- planetary motion model
Where was Ernest Rutherford from?
New Zealand
What were Rutherford’s conclusions?
- atoms have almost all of their mass concentrated in a very small positively charged region = the nucleus.
- the nucleus is surrounded by electrons which are at a relatively large distance.
What did the Planetary Motion Model demonstrate?
Electrons orbit around the nucleus like planets orbit around the sun. The nucleus held (only) protons (for the time being).
Who was Hans Geiger?
- a student of Rutherford.
- he was one of the people who had to spend long hours, in mostly darkness, counting the particles that hit the screen.
What did Geiger create?
He created the first electrical particle counter. He called it the Geiger counter.
What were Geiger’s contributions?
- determined that alpha particles were made up of 2 protons and 2 neutrons.
What did Irene Curie-Joliot and Frederic Joliot do?
- they bombarded beryllium with alpha particles, which created a beam of energy that has great power. It was able to penetrate metals.
- they thought it was a new form of energy; they thought that it was gamma rays.
What did Chadwick do with the Joliot’s research?
He found the the Curie-Joliot beam of energy was unaffected by magnetic fields- meaning it was neutral.
-particles moved at 1/10 the speed of light- so it was not radiant energy- it must be particles.
Who was James Chadwick?
He was a British Physicist and Chemist.
Who was credited with the discovery of the neutron?
James Chadwick
What were Chadwick’s particles?
- the new particles had approximately the same mass as a proton- but these new particles had no charge.
What was discovered after neutrons were discovered?
Isotopes of various elements were discovered.
What did Neil’s Bohr do?
He continued with energy calculations and he further developed the planetary motion model to include neutrons, and specific energies of electrons in a certain path. This is known as the Bohr’s model.
What is the order of the scientists?
Democritus of Abdera John Dalton William Crooke JJ Thomson Robert Millikan William Roentgen Henri Becquerel Marie & Pierre Curie Ernest Rutherford Hans Geiger Irene Curie-Joliot & Frederic Joliot James Chadwick Niels Bohr
