Atomic Structure Flashcards
What do atoms make up?
EVERYTHING!!!
What are the three particles atoms contain?
Electrons, neutrons and protons
What are the properties of a proton?
In the nucleus
Relative size=1
Relative charge=+1
What are the properties of a neutron?
In the nucleus
Relative size=1
Relative charge=0
What are the properties of an electron?
In the shells
Relative size=1 divided by 2000
Relative charge=-1
How big are atoms?
They are very small
They have a radius of 0.1 nanometres
What are isotopes?
Atoms with the same number of protons but a different number of neutrons. Some isotopes are radioactive
The atoms of an element always have the same number of what?
Protons
Scientists used to think that the atom was like a what?
Plum pudding- the atom was a sphere of positive charge with negative electrons spread throughout
What happened in Rutherford’s experiment?
He fired positively charged alpha particles at an extremely thin sheet of gold
What were they expecting to happen in the experiment?
For the particles to pass straight through the sheet.
What actually happened in the experiment?
Whilst most of the particles did go straight through the gold sheet, some were deflected more than expected, and a small number were deflected backwards. So the plum pudding model couldn’t be right
What did Rutherford come up with from this experiment?
There’s a tiny, positively charged nucleus at the centre, where most of the mass is concentrated. When alpha particles came near the concentrated, positive charge of the nucleus, they were deflected. If they were fired directly at the nucleus, they were deflected backwards. Otherwise, they passed through the empty space. Most of the atom is empty space
What else did Rutherford come up with from the plum pudding What experiment that later scientists proved was wrong?
That there is a ‘cloud’ of negative electrons that surround the nucleus- Scientists realised that electrons in a ‘cloud’ around the nucleus of an atom, as Rutherford described, would be attracted to the nucleus causing them to collapse.
Who discovered the electron?
JJ Thomson 1897
