Topic 4 - Atomic Structure Flashcards
What is definition of activity?
The rate at which an unstable nucleus decays.
What is an alpha paricle?
A positively charged particle consisting of two protons and two neutrons.
What is the an atomic number?
The number of protons found in an atom of a specific element. Each element has a different atomic number.
What is background radiation?
Radiation that is found in small quantities all around us and originates from natural sources such as rocks and cosmic rays, as well as from man-made sources such as nuclear weapons testing and accidents.
What is a becquerel?
The unit that is used for radioactive activity.
What is a beta particle?
A high speed electron that a nucleus emits when a neutron convert into a proton.
What is the Bohr model?
A model of the atom that suggested that electrons orbit the nucleus at set distances.
What is a chain reaction?
The process of neutrons released by a fission reaction, being absorbed by another unstable, large nuclei, and including further fission.
What is a count rate?
The number of decays that a detector measures per second.
What are electrons?
A negatively charged constituent of the atom, that are found in different energy levels, around the nucleus.
What are energy levels?
The states in which electrons are found in around a nucleus. Electrons can transition to a higher energy level through the absorption of electromagnetic radiation and can transition to a lower energy level through the emission of electromagnetic radiation.
What are fission products?
Fission produces two smaller nuclei, two or three neutrons and gamma rays. All these products are released with kinetic energy.
What are gamma rays?
Electromagnetic radiation emitted from a nucleus.
What is a Geiger-muller tube?
A detector that measures the count-rate of a radioactive sample.
What is half life?
The time it takes for the number of unstable nuclei of an isotope in a sample to halve, or the time it takes for the initial count rate of a sample of the isotope to halve.
What is an ion?
Atoms with a resultant charge due to the loss or gain of electrons.
What is irradiation?
The process of an object being exposed to nuclear radiation. The object doesn’t become radioactive.
What is an isotope?
Atoms with the same number of protons but different numbers of neutrons. The atomic number is the same, but the mass number is different.
What is the mass number?
The number of protons and neutrons in an atom.
What are negative ions?
Atoms that gained electrons and so have a resultant negative charge.
What is a neutron?
A neutrally charged constituent of the nucleus.
What are nuclear explosions?
Nuclear explosions in nuclear weapons are caused by an uncontrolled chain reaction which results in vast quantities of energy being produced in a very small period of time.
What is nuclear fission?
The splitting of a large and unstable nucleus into two smaller and more stable nuclei to produce energy.
What is nuclear fusion?
The joining of two small, light nuclei to form a large, heavier one and release energy.
What is the nucleus?
The positively charged centre of an atom, containing protons and neutrons.
What is the plum pudding model?
An old model of the atom that represented the atom as a ball of positive charge, with negative charges distributed throughout it.
What are positive ions?
Atoms that have lost electrons and so have a resultant positive charge.
What are protons?
A positively charged constituent of the nucleus.
What is radioactive contamination?
The unwanted presence of radioactive atoms on other materials. It is hazardous due to the decay of the contaminating atoms.
What is radioactive decay?
The random process involving unstable nuclei emitting radiation to become more stable.
What are sieverts?
It is the unit used for radiation dosage.
What is spontaneous fission?
Fission that occurs without the absorption of a neutron. Spontaneous fission is rare and in most cases, fission is induced with a neutron.
What did James Chadwick’s experiments on the atom prove?
The existence of neutrons.
Why do unstable nuclei give out radiation?
- Unstable nuclei undergo decay to become more stable
- As they release radiation their stability increases
State four type of nuclear radiation.
- Alpha Particles
- Beta Particles
- Gamma Rays
- Neutrons
What will stop beta radiation from passing through a point?
- A thin sheet of aluminium
- Several metres of air
What will stop gamma radiation from passing through a point?
- Several cm of lead
- A few metres of concrete
What radiation is the most and lease ionising?
Most ionising is alpha radiation.
Least ionising is Gamma Radiation.
Give 4 sources of background radiation?
- Rocks
- Cosmic Rays from Space
- Nuclear weapon testing
- Nuclear Accidents
State two uses of nuclear radiation in the field of medicine?
- Examining of internal organs
- Controlling destroying unwanted tissue
Explain the process of radiotherapy?
- Gamma emitters direct gamma rays at the cancerous cells
- The cancerous cells absorb the radiation and are killed
How are medical tracers chosen?
They should have a short half life and decay into a stable isotope which can be excreted. They should only release gamma radiation since it is weakly ionising and can easily pass through body tissue without damaging it.
What usually needs to happen to induce fission?
- The unstable nuclei must absorb a neutron
- Spontaneous fission is rare.
What form of energy do all fission products have?
They have kinetic energy.
What are the three main components of the core a nuclear reactor?
- Fuel Rods
- Control Rods
- Moderator
