A nucleus can be specified By an atomic number and a Mass number.
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Transcript of A nucleus can be specified By an atomic number and a Mass number.
The typical Nitrogen atom hasA mass number of 14.
It has 7 protons and 7 neutrons.
The atomic number never changes,However the mass can change.
All atoms are electrically Neutral, thus the number Of protons equals
the Number of electrons.
Symbol Name Explanation
A Mass Number The number of nucleons
Z Atomic Number The number of protons
N Neutron Number The number of neutrons
An isotope is when atoms of an Element having the same atomic
Number but different Neutron and mass number.
Hydrogen has 3 isotopes:HydrogenDeuterium
Tritium
Scientists measure Elements in AMU, or atomic
Mass units.
1 AMU = 1/12 (mass of Carbon)= 1.66 X 10-24 g
So, one proton or one Neutron are about
1 AMU each.
The strong nuclear force isAn attractive force that Overcomes the electrical
Repulsion between protons.
Nuclear reactions changeThe composition of An atoms nucleus!!
When a nucleus undergoes Nuclear decay, only three typesOf radiation can be released…
Alpha Beta
Gamma
NAME IDENTITY CHARGE PENETR-ATION
ALPHA
α
He-4
NUCLEI
2+ LOW
BETA
β
ELECTR-ONS
1- MEDIUM
GAMMA
γ
HIGH
ENERGY
X-RAY
NONE VERY
HIGH
Everybody thinks that this is so Hard, but there are only 2 rules…
The total of the atomic numbers on The left is that same as the total
On the right because chargeMust be conserved.
The total of the mass numbers on The left is the same as the total on
The right because mass must Be conserved.
131I 131Xe + 0β53 54 -1
This is the nuclear equationThat describes the beta Decay of iodine – 131.
The numbers ALWAYS balance!
One of the isotopes of radium, 226 Ra, decays by alpha
Emission. What is the resultingDaughter element?
88
226 Ra 222 Rn + 4 α88 86 2
As things decay, it can Be measured.
The SI unit of radioactivity isThe becquerel, Bq.
1 Bq = 1 decay per second
The half-life is the time requiredTo half the original nuclei
Of a radioactive material to Undergo radioactive decay.
T ½ = 0.693Decay constant
The 1/2 life of a radium nucleus is 5 X 1010s. A sample contains
3 X 10 16 nuclei. What is the decayConstant for this decay? How Many radium nuclei will decay
Per second?
Constant = 1.4 X 10-11
Activity = 420000 Bq
Stable nuclei can be made Unstable by bombarding them
With extra neutrons.
Heavy nuclei can undergoNuclear fission.
Nuclear fission is the breakingApart of a nucleus.
Light nuclei can undergo Nuclear fusion.
Nuclear fusion is when two Nuclei are squished together.
Stars work like this, up until Iron - 58, (the most stable element).Fusing elements after this require
Energy, thus are made in A supernova.
Many new particles have been Produced in accelerators.
There are 4 fundamental Interactions in nature…
Strong, Weak,Electromagnetic & Gravitational
A force can be thought of as Mediated by an exchange
Of particles.
Leptons are thought to be Elementary particles.
Hadrons include mesons & baryons.
Hadrons are thought to be madeOf quarks.
There are 6 quarks…
Up, Down, Charm,Strange, Top, Bottom.
The standard model can help Explain the early universe.