The Nuclear Atom Flashcards
Name and describe the experiment used to provide evidence for the existance, charge and size of the nucleus.
This is the aplha-particle scattering experiment. Alpha-particles are fired through a very thin sheet of gold foil, and onto a fluorescent screen where a visible flash of light is produced. This allows us to measure the angles at which the alpha-particles are deflected through the gold foil. Most alpha-particles were able to pass through the foil, indicating lots of empty space. Some alpha-particles were reflected over 90 degrees. This shows us that there is a nucleus of positive charge. These two observations together showthe the nucleus is very small (10^(-14)m).
Describe the basic structure of the atom.
A nucleus containing protons and neutrons have electrons orbiting round them.
How much smaller is the nucleus compared to the atom?
About 10^(4) - 10^(5) smaller.
In what instance do we use Coulomb’s Law?
When calculating the force of repulsion caused by the electrostatic force between protons.
In what instance do we use Newton’s Law of gravitation?
To calculate the attractive force between two masses. Inside the nucleus, this is the gravitational force.
Which is bigger, gravitational or electrostatic force inside the nucleus?
Electrostatic.
Give 5 points that describe the strong nuclear force.
1) It must be an attractive force that is larger than the electrostatic force in order to keep the particles together.
2) It has a short range - up to 10fm - the maximum size of the nucleus.
3) The strength quickly falls beyond this distance.
4) It works equally between all nucleons.
5) It must be repulsive at very small separations so the nucleus does not crush to a point.
How can we estimate the density of nuclear matter?
We calculate it’s volume and it’s mass, and then use the density equation. The volume can be calculated using it radius and v=(4/3)(pi)r^(3).
Define proton number.
The number of protons in a nucleus.
Define nucleon number.
The number of nucleons in a nucleus - this includes protons and neutrons.
Using standard notation, which way round are the proton number and nucleon number written?
The nucleon number on the top, and the proton number on the bottom.
Define the term isotope.
Atoms of the same element with the same number of protons but different numbers of neutrons.
Why does nuclear decay occur?
So a nucleus can become more stable.
What are the quantities conserved in nuclear decay?
Energy, momentum, proton number, charge, nucleon number.
What is not conserved during nuclear decay?
Mass - some is converted into energy.
