P1.1 - the particle model 1

• Who were the two greek philosophers who thought that you could no longer cut anymore paper and you would have an atom

  Democritus and Leucippus
• What did Democritus and leucippus say the atom was?

  Too small to see
• For many years , ideas about atoms did not develop due to what?

  Having no instruments to measure atoms
• In what year did John Dalton do experiments to measure how elements combined?

  1870s
• What did John Dalton think would explain the results of his experiments?

  if everything is made of atoms
• His model of an atom was a very small indestructible sphere. What did it look like?


  This model

  
• What did John dalton think?

  • All the atoms in an element are the same
  • The atoms in one element are different from the atoms in all other elements
• in 1897 what was Thomson investigating?

  The rays given out by hot metals
• What was the name given to the rays emitted by the hot metals in Thomsons investigation in 1897?

  Cathode rays
• What was Thomson not investigating in his experiment of rays given out by hot metals

  atoms
• What did Thomson discover?

  That cathode rays are made of particles that are called electrons that must have come from inside an atom. He also worked out that the charge on an electron is negative
• What two ideas had Thomson made sense of?

  • That an Atom contains negative electrons
  • overall , atoms have no electrical charge they are neutral
• What year did Thomson suggest a new model?

  1904
• What was this new model called

  Plum pudding model
• In the plum pudding model What is the atom to be thought to consist of?

  a Positive mass with negative electrons embedded in it

  
• What did he think that the positive mass might be like?

  a solid or like a cloud