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Nuclear Decay Properties

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rebecca simpson

on 15 October 2014

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Transcript of Nuclear Decay Properties

fig. 1
Lets look at radiation in a little more detail
Radioactive Decay
Alpha
Beta
Gamma
What Is It?
What Happens?
Properties
What is it?
What Happens?
Properties
What Is It?
What Happens?
Properties
3 types of decay
Helium Nucleus
2 protons
2 neutrons
relatively LARGE and SLOW MOVING
Alpha decay usually occurs in heavy nuclei such as uranium or plutonium
A nucleus emits an alpha particle to become more stable
How can we seperate Radioactive rays?
Mass number
(Protons and Neutrons)
Atomic Number
(Protons)
An Alpha particle ALWAYS has a mass number = 4 and Atomic number = 2
NOTE: The highlighted lines on the left ALWAYS add up to the highlighted lines on the right
Because alpha particles are charged and relatively heavy, they interact intensely with atoms in materials they encounter, giving up their energy over a very short range. In air, their travel distances are limited to no more than a few centimeters.
Ionisation
Because they are heavy they do not travel far through any material
Ionization is the process where electrons are given enough energy to be removed from the atom that they are attached to. This leaves the atom with less negative charge and it becomes an ION.
Alpha radiation was the most ionising why do you think this is?
Alpha decay consists of 2 protons and 2 neutrons (Helium nucleus)
it is highly ionizing because they strongly attract electrons
have a charge of +2
bent by electric and magnetic fields but not as much as beta due to larger mass
relatively heavy and slow moving
absorbed by skin / 5cm air / card therefore it has poor penetrating power
Beta particles are electrons
Made up of an electron
Negatively charged
Fast Moving
Difficult question....
Where does the electron come from?
ANTINEUTRINO
Beta emission is accompanied by the emission of an electron antineutrino which shares the momentum and energy of the decay.
The high energy electrons have greater range of penetration than alpha particles, but still much less than gamma rays.
Why do you think the Beta Particle bends the most?
a fast moving electron
in beta radiation, a neutron turns into a proton and an electron and the electron is ejected
very light (little mass)
weak ionizing ability
move at 9/10 the speed of light
bent strongly by electric and magnetic fields
fast moving, moves up to 30-50cm in air, absorbed by 5mm Al. Can ionize an air molecule
Electromagnetic Rays
electromagnetic rays
moves at the speed of light
high energy radiation with shorter wavelength than X rays
never fully absorbed therefore has a very long range
very very weakly ionizing because it has no charge or mass
not affected by electric and magnetic fields
kills living cells
only emitted with alpha and beta particles
strength halved by thick concrete, thick lead (25mm)
No Mass and No Charge.... This means that the element does not change after decay
VERY high frequency so HIGH energy
E = hf
A Gamma ray is emitted after either BETA or GAMMA decay leaves the daughter nucleus in an EXCITED state as the nucleus moves to a ground state the nucleus emits energy in the form of a high energy PHOTON
Gamma rays are very poor at ionising (about 1 to 1) but they are very difficult to stop (they are very penetrating). As they are not good ionisers, they are less dangerous to life.
NO CHANGE IN THE ELEMENT OR THE NUMBER OF PROTONS OR NEUTRONS
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