Atomic structure Flashcards
Who was Democritus?
A Greek who said that all matter was made up of identical lumps called “atomos”.
Who was John Dalton?
In 1804, he agreed with Democritus, he thought that each element was made up of a different kind of atom and that atoms couldn’t be broken up
Who was J J Thompson?
About 100 years later (after Dalton), he discovered electrons could be removed from atoms. He suggested atoms were spheres of positive charge with negative electrons stuck in them like plums in plum pudding
What did Rutherford do? What was he expecting to see?
He got 2 of his students; Geiger and Marsden to fire a beam of alpha particles at thin gold foil. They expected the positively charged alpha particles would be slightly deflected by the electrons in the foil
What actually happened in Rutherford’s experiment? What did this mean?
Most of the alpha particles went straight through the gold but the odd on came back. This meant most of the mass of an atom was a the centre in a tiny nucleus. They realised the nucleus has a positive charge as repelled the positive alpha particles
Also showed that most of an atom is empty space
They came up with the Nuclear model for an atom
In the nuclear model, the [ ] is tiny but it makes up most of the [ ] of the atom. It contains protons and [ ] - overall positive charge
The rest of the atoms is mostly empty space. The [ ] whizz around the nucleus. They give the atom its overall size - the radius of the atom’s nucleus is about [] times smaller that the radius of the atom
nucleus mass neutrons electrons 10,000
State the mass and charge of each particle in an atom
Proton ; 1 (mass) and +1 (charge)
Neutron; 1 (mass) and 0 (charge)
Electron; 1/2000 (mass) and -1 (charge)
