Atoms and the Periodic Table Flashcards
In early models, what were atoms thought to be?
They were thought to be tiny spheres that could not be divided into smaller particles
What did Thomson discover?
And in what year?
Thomson discovered the electron and therefore the representation of the atom had to be changed
In 1898.
What is the overall charge of an atom?
Neutral (it has no charge)
What was the name for Thomson’s model?
And what did it depict?
Plum pudding model
It showed that atoms contained tiny, negative electrons surrounded by a sea of positive charge.
Who came up with the plum pudding model?
Thomson
Who bombarded a thin sheet of gold with alpha particles?
Geiger and Marsden
What experiment did Geiger and Marsden carry out?
What did this experiment show?
They bombarded a thin sheet of gold with alpha particles
Most of the positively charged alpha particles passed straight through the atoms
But a tiny number were deflected back to the source
Who looked at the results from Geiger and Marsden’s experiment?
Rutherford
What did Rutherford conclude?
After looking at Geiger and Marsden’s experiment, he concluded that the positive charge in an atom must be concentrated in a very small area (the nucleus)
What is Rutherford’s model named?
The nuclear model - because he essentially discovered the nucleus
What did Bohr deduce?
That electrons must orbit the nucleus at specific distances - because otherwise, they would spiral inwards
Who deduced that electrons must orbit the nucleus at specific distances?
Bohr
What is the nucleus made up of?
And what charges do they have?
Protons - positive charge
Neutrons - no charge
What is the typical atomic radius?
About 0.1 nanometres (nm) or 1 x 10 ^ -10 m
What is the relative mass and relative charge of …
- a proton
- a neutron
- an electron
relative mass relative charge
proton 1 +1
neutron 1 0
electron very small -1
