The Atom chapter1 Flashcards
What did Dalton put forward
The atomic theory
What was daltons atomic theory?
- All matter is made up of very small particles called atoms
- All atoms are indivisible. They cannot be broken down into simpler particles
What did William Crookes do?
He discovered Cathode Rays
Made the “vacuum tube” and “Crookes paddle wheel” which deduced the following properties of cathode rays
- They travel in straight lines
- They cause glass to fluoresce
- They have enough energy to move a paddle wheel.
(CNAP-Cathode Negative. Anode Positive)
Who discovered the electron?
JJ. Thompson
How did JJ Thompson discover the electron?
Thompson passed cathode rays through a small hole (anode plate) and the narrow beam of cathode rays passed two magnetic plates ( + and -)
The cathode rays were attracted to the positive plate so Thompson concluded that they consisted of negatively charged particles.
These negative particles were known as electrons ( the name was given by George Stoney)
Who determined the size of the electron and how?
Robert Millikan
How:
•Sprayed tiny oil droplets between two charged metal plates
•Used X-rays to ionise air between the plates (molecules in the air lost electrons and formed ions)
•As the oil droplets fell through the air they picked up these electrons and the oil drops became negatively charged
•Millikan carefully adjusted the charge of the plates until the oil droplets were stationary.
•He then found the size of the charge of the electron
E/M=1.76x10’’
What was the name of Thompsons Model of the Atom called? What did it look like?
Plum pudding
Thompson imagined an atom as a sphere of positive charge with negative electrons embedded in it at random
Who discovered the Nucleus?
Ernest Rutherford
How did Rutherford discover the nucleus
Radioactive Source–>(alpha particles)
Alpha particles–>Thin gold foil–>fluorescent screen.
1. *Observation* •Most alpha particles pass through the foil foil *Conclusion* •Most of the atom is empty space
2.
Observation
•Some alpha particles are deflected at large angles
Conclusion
•They repel when they pass near the small positive nucleus ( positive)
3.
Observation
•Small number of particles reflected back along their own paths
Conclusion
•Small number of alpha particles collide head on the nucleus ( very small)
How was Rutherford’s works be summarised?
- He discovered that the atom consist of a small dense positive core called the nucleus
- He discovered that positive particles called protons were located on the nucleus
- New structure of the atom was it consisted of a nucleus and that electrons were in some sort of ‘electron cloud’ surrounding the nucleus
Who discovered the neutron?
James Chadwick
How did James Chadwick discovery the Neutron?
He bombarded beryllium with alpha particles
Then neutrons came out of the beryllium
He concluded that the alpha particles were knocking neutral particles out of the nucleus of the beryllium atom
He found that these particles had the same mass as the proton and because they were neutral he called them neutrons
What did each of these men do/discover:
- John Dalton
- William Crookes
- JJ Thompson
- George Stoney
- Robert Millikan
- Ernest Rutherford
- James Chadwick
- Atomic Theory
- Cathode rays (electron)
- Electron
- Name of electrons
- Size of charge of electron
- Nucleus
- Neutron
What is the spreading of particles called?
Diffusion
What’s the law of conservation of mass
States that matter is neither created nor destroyed in the cause of a chemical reaction
