P1.1 - The Particle Model Flashcards
Which Greek philosophers first thought of the atom?
Democritus and Leucippus
What does atomos mean in Greek?
Indivisible
What did the Greek philosophers believe about the atom
It was too small to see
Eventually you could not cut up paper anymore and you would get an atom
In What year was Dalton doing his experiment?
1870s
What experiment was Dalton doing?
He was doing experiments to measure how elements combined
Describe daltons model
A very small indestructible sphere
What did Dalton think about atoms
All atoms in one element are the same
The atoms in one element are different from the atoms in all other elements
When was Thomson investigating cathode rays
In 1897
What did Thomson discover
He discovered an electron and found out that it had a negative charge
What did Thomson find out about the atom?
An atom contains negative electrons
Overall atoms have no charge. They are neutral
When did Thomson suggest his new model
In 1904
What was the name of Thomson’s new model
The plum-pudding model
Describe the plum pudding model:
The atom consists of a positive mass (like a cloud) with negative electrons embedded in it.
How does the history of the atom link to idea change
The history of the model of the atom shows that ideas change when there is new evidence that cannot be explained using old ideas
In what year was the Rutherford model discovered
1899
What was Rutherfords experiment
They fired a
Describe Rutherfords Experiment
He decided to fire alpha particles at a piece of gold foil
The alpha particle source was in a lead box with a narrow hole white a fixed thin metal foil placed in front of it.
The apparatus above was in an evacuated chamber to prevent air molecules absorbing the alpha particles
There was a detector outside of the chamber and everytime an alpha particle hit the glass plate, there was a spot of light.
The detector was moved to different positions and they counted the number of spots of light that they saw.
Describe Rutherfords model of the atom
An atom is made up of a tiny positively charged nucleus with electrons around the outside.
Almost all of the mass of an atom is in its nucleus
What was the problem with the plum pudding model
You would expect the electrons to spiral until they hit the nucleus
Describe Bohrs model
Electrons can only move in fixed orbits called electron shells around the nucleus
How big is an atom
1 ✖️10^-10
What is an order of magnitude
Anything to the nearest power of 10
How do you calculate the length of a molecule
Number of atoms ✖️10^-10 m/atom
