P1.1 Flashcards
What did Democritus and Leucippus say?
They said that if you kept cutting paper you would reach a point where you cannot cut any more, which is an atom.
Why did ideas about the atom take a very long time to develop?
There was very little evidence and equipment that could be used
People were very religious
What was John Dalton’s model? (3marks)
The atom is a small, indestructible sphere
All atoms of an element are the same
All atoms in one element are different from atoms in another element
What was JJ Thomson investigating and what did he discover?
He was investigating cathode rays given out by metals. He discovered that they were made up of electrons which had a very low mass and that it was negative
What was JJ Thomson’s model?
The plum pudding model:
An atom was a positive mass(cloud) with negative electrons embedded inside like raisins in a pudding.
Overall the atom was neutral and contained negative electrons
What was Rutherfords Experiment?
He fired alpha particles which have a positive charge at a piece of gold foil, with the help of Hans Geiger and Ernest Mardsen. He expected all the particles to pass straight through but some of them deflected to the side and some bounced back
Describe Rutherford’s theory
He suggested that the atom was made of a dense, positively charged nucleus with electrons orbiting around the outside. These were later called protons.
Explain the results of the gold foul experiment
Positively charged alpha particles are attracted to negative electrons so they pass through. Protons and neutrons repel alpha particles which causes them to bounce back or deflect
What was Bohr’s model?
His model said that electrons orbited the nucleus in fixed shells at fixed levels. This was because the problem with the previous model was that electrons would be attracted to the nucleus and collapse in on itself
Who discovered the neutron
Chadwick
What is a molecule?
A collections of atoms bonded together
What is the diameter of an atom?
1x10^-10
Describe the structure of an atom
An atom consists of a nucleus which contains positive protons and neutral neutrons so it has an overall positive charge. Negative electrons orbit the nucleus at fixed orbits
