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Atomic and Nuclear Physics
Terms in this set (40)
What is the Plum Pudding Model
The atom is a positive sphere with negatively charged electrons embedded in it. Evenly spread. Overall neutral. Spaces between atoms.
What is Thomson's Experiment?
A Crookes tube was used to discover the subatomic particle, the electron. Apparatus used to identify cathode rays as negatively charged particles, electrons. Thomson found the electrons mass to be at least 1000x smaller than atoms.
What is Rutherford's Gold Foil Experiment?
Alpha particles were passed through a thin piece of gold foil, (a few atoms thick). Carried out in a vacuum. Proved Thomson's Plum Pudding Model wrong.
What are Rutherford's Observations and Justifications?
Nearly all alpha particles went straight through the gold foil. (Most of an atom is empty space with a very small nucleus). 1 in 8000 alpha particles were deflected through a wide range of angles. (The nucleus pushes the alpha particles away with an electric force. Therefore, the nucleus is positively charged because the alpha particles are positively charged, like charges repel.) Of the deflected alpha particles some of those were deflected directly back. (For the deflection directly back, the nucleus must be massive/very dense.)
What is the Rutherford Model?
The atom is overal neutral. The atom is made up of a positive nucleus consisting of protons. There are spaces within atoms. Electrons orbit the positive nucleus at a distance.
What are isotopes?
Atoms with the same number of protons but different number of neutrons. same chemical property different mass.
What is a subatomic particle?
Any particle smaller than a hydrogen atom.
What is the meaning of radioactive?
Emitting or emission of ionizing radiation or particles.
What is background radiation?
The nuclear radiation that arises naturally from cosmic rays and from radioactive isotopes in the soil and air.
What is nuclear radiation?
Energy particles or rays that are given off from a radioactive element such as Uranium, as it decays.
How do photographic plates detect radiation?
When alpha, beta and gamma radiation hits photographic film it causes a chemical reaction to take place. This causes the film to go black (fogging). The amount of fogging indicates the intensity of the radiation.
How do film badge dosimeters detect radiation?
Small piece of photographic film is covered by filters. (Thin plastic, copper and aluminium) Filters identify the type and intensity of the radiation.
How does the Geiger Muller Tube detect radiation?
A pulse of charge is produced when radiation enters which can be amplified and counted making the familiar sound of a GM counter. The GM counter measure the number of radiation emissions detected each second or minute.
What is the mass of an alpha particle?
What is the mass of a beta particle?
What is the mass of a gamma particle?
What is the charge of an alpha particle?
What is the charge of a beta particle?
What is the charge of a gamma particle?
What is the speed of the alpha particle?
5% of the speed of light.
What is the speed of the beta particle?
99% of the speed of light.
What is the speed of a gamma particle?
The speed of light 3x10^8
What is an alpha particle?
Helium nucleus made up of 2 protons and 2 neutrons which has a very high ionizing power but a low penetrating power as it is stopped by a few cm of air or thin sheet of paper.
What is a beta particle?
High kinetic energy electron which has moderate ionizing power and a medium penetrating power as it is stopped by a few mm of most metals such as aluminium.
What is a gamma particle?
Very high frequency electromagnetic radiation which has a low ionizing power and a high penetration power as it is stopped by several cm of steel or meters of concrete.
How are alpha particles deflected by a magnetic field?
Deflected weakly in the opposite direction to the way electrons would be deflected because they are heavier and positive.
How are beta particles deflected by a magnetic field?
Deflected strongly because they have a small mass and negative charge like electrons.
How are gamma particles deflected by a magnetic field?
Not deflected at all because they are not charged particles.
How are alpha particles deflected by an electric field?
Deflected towards the negative plate because they're positively charged.
How are beta particles deflected by an electric field?
Deflected more strongly towards the positive plate because they're lighter negative particles.
How are gamma particles deflected by an electric field?
Not deflected at all because they are not charged particles.
What is radioactivity?
Particles which are emitted spontaneously and randomly from nuclei as a result of nuclear instability.
What is 'half life' of a radioisotope?
The time taken for half the undecayed atoms in a sample to disintegrate and is taken as a measure of the rate of decay.
Why is the source of the alpha particle at the end of a narrow lead tube?
To provide a narrow beam for the alpha particle/to direct the alpha particle/ensure hitting perpendicular to the gold foil.
Why is Rutherford's Gold Foil Experiment carried out in a vacuum?
Alpha particles will not travel far as they will be stopped and lose energy when they collide with air particles.
Why is there a Zinc Sulfide screen in Rutherford's Experiment?
Alpha particles aren't visible to the naked eye. The ZnS coating will show when alpha particles strike it.
What is ionization?
Radiation 'knocks' electrons out of atoms turning the atom into ions. Causing the atom to become charged.
Why is the shape of the Rutherford's Gold Foil Experiment circular?
Enables detection of particles that may be deflected in any direction.
Why it is necessary for the sheet of gold foil to be only a few atoms thick?
If the foil was too thick the alpha particles would just be absorbed. Maybe even by a few cm of air.
Why is it necessary for the half-life of radioisotopes to be injected into people to have a very short time?
So we do not have a harmful amount of radiation exposure. May cause damage to tissues.
THIS SET IS OFTEN IN FOLDERS WITH...
Physics Exam 4 (4)
CHAPTER 11 HW (PHYSICS)
CHAPTER 12 HW (PHYSICS)
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