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RADIOACTIVITY
PENGENALAN ASTRONOMI
DAN
FIZIK MODEN
GROUP ASSIGNMENT
GROUPMEMBERS :
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Radioactivity
When an unstable nucleus releases energy and/or particles.
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Radioactive Decay
There are 4 basic types ofradioactive decay
Alpha Ejected Helium
Beta Ejected Electron Positron Ejected Anti-Beta
particle
Gamma Ejected Energy
You may encounter protons andneutrons being emitted as well
n
p
e
e
He
1
0
11
0
0
0
1
0
1
4
2
K
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Alpha decay is a type of radioactive decay
in which an atomic nucleus emits an alpha
particle and thereby transforms (or
'decays') into an atom with a mass number
4 less and atomic number 2 less.
For example:
4238 234 + 2He2+
92 90Th [1]
238 234
U Th + a
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.
An alpha particle is the same
as a helium-4 nucleus,
and both mass numberand
atomic number are the same
Alpha decay is by far the most common form of cluster
decay where the parent atom ejects a defined daughter
collection of nucleons , leaving another defined product behind
(in nuclear fission , a number of different pairs of daughters
of approximately equal size are formed).
Alpha decay is the most likely
cluster decay because of the
combined extremely high binding
energy and relatively small mass of the
helium-4 product nucleus (the alphaparticle).
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In nuclear physics, beta decay is a type of radioactive decay in which a beta particle (anelectron or a positronis emitted
In the case of electron emission, it is referred to as beta minus (), while in the case of apositron emission as beta plus (+)
In electron emission, an electron antineutrino is also emitted, while positron emission isaccompanied by an electron neutrino. Beta decay is mediated by the weak force.
Emitted beta particles have a continuous kinetic energy spectrum, ranging from 0 to themaximal available energy (Q), which depends on the parent and daughter nuclear states thatparticipate in the decay. A typical Q is around 1 MeV, but it can range from a few keV to afew tens of MeV. Since the equivalence of energy of the rest mass of electron is 511 keV, themost energetic beta particles are ultrarelativistic, with speeds very close to the speed of light
Sometimes electron capture decay is included as a type of beta decay (and is referred to as
"inverse beta decay"), because the basic process, mediated by the weak force is the same.However, no beta particle is emitted, but only an electron neutrino. Instead of beta-plusemission, an inner atomic electron is captured by a proton in the nucleus. This type of decay istherefore analogus to positron emission (and also happens, as an alternative decay route, in allpositron-emitters). However, the route of electron capture is the only type of decay that isallowed in proton-rich nuclides that do nothave sufficient energy to emit a positron (andneutrino). These may still reach a lower energy state, by the equivalent process of electron-capture and neutrino-emission.
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There are3 different modes of beta decay
Electron
emission
Electron capture
Position
emission
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Electron emitters are found
throughout the periodic table, from
the lightest elements (3H) to the
heaviest (255Es).
Electron
emission
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Electron capture
Leads to a decrease of one in the charge on the nucleus.
The energy given off in this reaction is carried by an x-ray
photon, which is represented by the symbol hv, where h is
Planck's constant and v is the frequency of the x-ray
The product of this reaction can be predicted, once
again, by assuming that mass and charge are
conserved.
The electron captured by the nucleus in this reactionis usually a 1s electron because electrons in this
orbital are the closest to the nucleus.
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Positron
emission