fun7.1 the nuclear atom notes
TRANSCRIPT
FUNDAMENTAL Physics – Atomic Physics: 7.1 The Nuclear Atom
The Atom
http://www.youtube.com/watch?v=DwqYsoDqbCQ
Learning Objectives
I can describe the Geiger-Marsden Experiment
I can describe how these results explain Rutherford’s Model of the nuclear atom
I can define a nucleus in terms of Proton Number and Nucleon Number
I know how ISOTOPES occur
I know that some isotopes are UNSTABLE and undergo a RANDOM process of radioactive decay
I know that Alpha, Beta and Gamma radiation is emitted when an unstable nucleus decays
I know the nature of Alpha, Beta and Gamma radiation and their defferent penetration
The Scientific Process
Phenomena hypothesis prediction investigate/experiments theory
Law
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FUNDAMENTAL Physics – Atomic Physics: 7.1 The Nuclear Atom
Earlier Models of the Atom; JJ Thompson – Plum Pudding
Geiger-Marsden Experiment – Alpha Particle Scattering by a Gold Foil
The results of this experiment were:
The large majority of the alpha particles go straight and are not deflected
A small number of alpha particles are deflected through a small angle.
A very small number of alpha particles are deflected through a large angle (rebound)
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Florescent screen Large majority of flashes occur straight ahead
Small number of α particles are deflected
Very small number of α particles deflected at a large angle
FUNDAMENTAL Physics – Atomic Physics: 7.1 The Nuclear Atom
Rutherford’s Model of the Nuclear Atom
The observations from the Geiger-Marsden experiment were used by Rutherford and led him to propose the theory of the nuclear atom.
Observation from the
Geiger-Marsden Experiment
Hypothesis proposed by Rutherford
Large majority of the particles go straight through the gold leaf
Most of an atom is ......... space and therefore the mass of the atom must be held in a small region, called the ..........
Some of the particles are scattered.
No useful hypothesis can be considered.
A very small number of positively charged particles undergo LARGE ANGLE SCATTERING. (repelled back through more than 90o)
There must be a …….., …………… charged nucleus, that contains almost all of the ………….. of the atom.
Other advancements (not required):
Niels Bohr postulated the quantum energy levels of the electrons.
1932 Neutrons discovered by James Chadwick.
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FUNDAMENTAL Physics – Atomic Physics: 7.1 The Nuclear Atom
What Affects the Scattering of the Alpha Particles (required)
What affects the amount of deflection?
1. Charge – the alpha particles are positively charged that is why they experience ............... from the ............ charged nucleus.
2. Speed – Particles B and F are moving ............... than particle A. They experience a smaller deflection because they spend ........... time close to the nucleus.
3. Proximity to the nucleus – only the very small number of alpha particles that pass very close to the ............. experience enough repulsion for ‘large angle scattering’ such as particle D.
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FUNDAMENTAL Physics – Atomic Physics: 7.1 The Nuclear Atom
The Rutherford-Bohr / Standard Model of the Atom
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Positive
protons
Neutral
Neutrons
Negative electrons
FUNDAMENTAL Physics – Atomic Physics: 7.1 The Nuclear Atom
Atomic Symbols
Eg. Carbon
Z for example 6 is the proton number / atomic number, which is the number of protons in the nucleus. The proton number defines the element.
A, for example 12 is the mass number / nucleon number which is the number of protons plus neutrons in the nucleus.
Isotopes
A given element is defined by the given number of protons. However the number of neutrons can change. An isotope is different version of the same ……….. that
has a different number of …………….
Radio-isotopes
Since neutrons play an important role in binding the nucleus together, too ……… or too ……… neutrons will affect the stability of the nucleus.
A radio-isotope has an unstable nucleus that can, at any moment, decay in order to try and achieve stability.
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C12
6CA
Z
FUNDAMENTAL Physics – Atomic Physics: 7.1 The Nuclear Atom
Radioactive Decay
Decay is a random process by which an alpha or beta particle or a gamma photon is emitted from an ………….. nucleus which is trying to become stable.
Radioactive Particles
http://www.youtube.com/watch?v=N8JRqW1-my4&NR=1
http://www.youtube.com/watch?v=9j62CVRwZPc
Name Symbol Nature Sources Ionising Power
Penetration Stopped by
Range in air
Alpha ………..
Nucleus
4He2+
Larger nuclei
Eg. 208Po
High Low ……… 2-3cm
Beta An ………
-1-1
smaller nuclei
eg. 40K
Medium Medium1-2cm of ……..
Few feet
Gamma γ
An EM wave. A
packet of …….
called a PHOTON.
Eg. 99Tclow high
Several inches of …….
kms
Homework Page 253 Q 1-47
FUNDAMENTAL Physics – Atomic Physics: 7.1 The Nuclear Atom
For this topic please make use of www.furryelephant.com which has many electricity animations and explanations.
School username: islandschoolSchool password: islandscience
This was expensive, but it is very very good.
The Wall
http://www.youtube.com/watch?v=M_bvT-DGcWw
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FUNDAMENTAL Physics – Atomic Physics: 7.1 The Nuclear Atom
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