Nucleus of atom consist of….
Neutrons = uncharged
Protons = positive charge
What is the principal role of the neutrons in an atomic nucleu
Is to act as a sort of nuclear cement to hold the nucleus together
Explain Nucleons
- Are bound together by an attractive nuclear force appropriately called the strong force
- The nuclear force of attraction is strong only over a very short distance (large force vectors)
- When two nucleons are just a few nucleon diameters apart, the nuclear force they exert on each other is nearly zero (small force vectors)
Explain Electrostatic force
Acts as a repulsive force between protons that are not in direct contact with one another
Explain Electrostatic force and Nucleons
- Nucleus stays intact, stable if nuclear forces over rules electrostati forces
- With heavier nuclei, charges separated more, nuclei becomes unstable
- Unstable nuclei, can become stable by: - radioactive disintegration - decay - stable nuclei and radioactivity
Explain Radioactive Isotopes
- Isotopes of an element are chemically identical but differ in the number of neutrons
- In a neutral atom, the number of protons in the nucleus determines the number of electrons surrounding the nucleus
- The lower number in each notation is the atomic number or the number of protons.
- The upper number is the atomic mass number or the total number of nucleons in the nucleus
What are the Types of natural radioactive decays
The atoms of radioactive elements emit three distinct types of radiation called alpha radiation, beta alpha radiation, and gamma alpha radiation
Explain Beta radiation
Beta particles are negative, very energetic electrons from nucleus: (1MeV), An electron is ejected from the nucleus when a neutron is transformed into a proton
Explain Alpha radiation
- Alpha particles have a positive electric charge
- They are made of 2p, 2n, and is identical to the nucleus of a He atom or nucleus. (several MeV)
Explain Gamma radiation
Gamma particles are electrically neutral and is massless energy. They are photons but of much higher frequency and energy. (10’s to 100’s MeV)
Explain Radiation Penetrating Power
- The penetrating power of radiation depends on its speed and its charge
- There is a great difference in the penetrating power of the three types of radiation
- Alpha particles are the easiest to stop - they can be stopped by a few sheets of thin paper
- Beta particles go right through paper but are stopped by several sheets of aluminum foil
- Gamma rays are the most difficult to stop and require lead or other heavy shielding to block them
Pretend you are given three radioactive cookies—one alpha, one beta, and the other gamma. Pretend that you must eat one, hold one in your hand, and put the other in your pocket. Which would you eat, hold, and pocket if you were trying to minimize your exposure to radiation ?
If you must, then hold the alpha; the skin on your hand will shield you
Put the beta in your pocket; your clothing will likely shield you
Eat the gamma; it will penetrate your body anyway. (In real life, always use appropriate safeguards when near radioactive materials.)
Explain all ionizing types of radiation
- Interact with atoms, remove electrons, displace atoms
- Can break nuclei apart
Environmental effects: Biological tissue of radioactive radiation
- Complex molecular structures easily damaged
- Breaking bond local damage to DNA, cell structures
- Damage is permanent adds up
- Long term effect cause cancer growth
What are the Types of natural radioactive radiation : radioactivity
- Exposure at low dose over long periods
- Increased dose over shorter period
- Other radiation: Neutrinos, Cosmic rays
Explain the Types of natural radioactive radiation : radioactivity
- Exposure at low dose over long periods :
- Body can regenerate and remove damaged material
- Damage can be repeated in DNA – transfer to offspring - Increased dose over shorter period :
- Damage cannot be removed in time, radiation illness - Other radiation: Neutrinos, Cosmic rays
- Very high energies (Mev to GeV)
- Highly penetrating, minimum interaction
How can radioactivity be measured
- At source – amount of radiation released
- At observation point – amount of radiation absorbed
Explain radioactivity being measured at the source
- Intensity of radioactive radiation is measured in Becquerel (Bq)
(Activity of a specimen is the number of disintegrations per second)
1 Curie (Ci) = 3.7 x 1010 Bq
Explain radioactivity being measured at observation point / receiver
Amount of absorbed energy from radioactivity (dose) is measured in gray (Gy)
Explain Radioactive Half-Life
- Since some radioactive nuclei are more stable than others, they decay at different rates
- A relatively stable isotope will decay slowly, while an unstable isotope will decay in a shorter period of time
- The radioactive decay rate is measured in terms of a characteristic time, the half-life
- The half-life of a radioactive material is the time needed for half of the radioactive atoms to decay
Explain The half-life T1/2
- is the time needed for half of the radioactive atoms to decay
- To get the relation between the half-life and the decay constant, N/No is set to 1/2 and t = T1/2
If a sample of a radioactive isotope has a half-life of 1 year, how much of the original sample will be left at the end of the second year? What happens to the rest of the sample?
- One quarter of the original sample will be left
- The three quarters that underwent decay became other elements
A certain isotope has a half-life of 10 years. This means the amount of that isotope remaining at the end of 10 years will be :
A. zero.
B. one-quarter.
C. half.
D. the same
Half
Wat is Radioactive Fallout
- Deposition of radioactive particles on the surface of the earth caused by nuclear fission
It is released into the atmosphere through mainly two ways:
➢ Nuclear explosions
➢ Nuclear energy conversion plants such as Koeberg, Chernobyl etc.
