P1.1 - The Particle Model Flashcards
What was John Dalton doing in the 1870s?
Performing experiments looking at how different elements combined.
What are atoms?
Atoms are particles, that combine with each other in different ways (form bonds) to make up all matter in the universe.
What was J.J. Thompson investigating in 1897?
Rays given out by hot metals (cathode rays)
What was the view of Greek philosophers?
Gave the name atom to what they thought was to be the smallest particle in nature. ‘Atomos’ - ‘Indivisible’
How did Dalton explain his results?
Dalton proposed all matter (i.e. - everything) was made up of tiny, indivisible particles called “atoms”.
What were the three main points in Dalton’s model of the atom?
- Atoms were very small, indivisible/indestructible
spheres. - All the atoms in an element are the same.
The atoms in one element are different from the atoms
in all other elements.
What did Thompson discover from his experiment?
- A small (<1/100th the size of a hydrogen atom)
- Negatively charged particle which he called the
electron
What was J.J. Thompson’s conclusion and why?
He proposed that atoms weren’t indivisible, but were made up of other particles
What two ideas does J.J. Thompsons plum-pudding model of the atom make sense of?
1. An atom overall has no
electrical charge. They are
neutral.
2. An atom contains negative
electrons.What are the properties of J.J. Thompson’s plum-pudding model of the atom?
Positively charged mass spread evenly out with negatively electrons embedded randomly in it.
What famous experiment did Ernest Rutherford carry out in 1899?
The Alpha Scattering Experiment
Describe the details of the alpha scattering experiment.
- Everything in an evacuated chamber. - Alpha particle source in a lead box with a narrow hole. - Alpha particles fired at a piece of gold foil. - A detector which consisted of a microscope focused on a small glass plate was moved in different positions. - The scientists counted the number of spots of light they observed in a certain time.
Why was the alpha scattering experiment apparatus in an vacuum chamber?
To prevent air molecules absorbing the alpha particles.
Why was a sheet of gold foil used?
Gold foil is one/very few layer of atoms thick.
What were the results of the alpha scattering experiment?
- Most alpha particles passed straight through the foil. - Few alpha particles deflected through small angles. - Very few alpha particles deflected through more than 90 degrees (were turned back).
