Topic 7: Atomic, Nuclear and Particle Physics Flashcards

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1
Q

Thomson’s Plum Pudding Model

A

Atoms were thought to be a cloud of positive charge with negative charges embedded in it (like a chocolate chip muffin).

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2
Q

Describe Rutherford’s experiment (method + expected results/actual results)

A

Alpha particles (helium nuclei) were fired at a thin gold foil. A fluorescent screen detected where they went.If Thomson’s model was correct the alpha particles would pass straight through undeflected (as the charge was supposedly evenly distributed throughout the atom). Most alpha particles were undeflected, a few were deflected slightly and a few bounced straight back.

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3
Q

What did Rutherford’s experiment conclude?

A
  • That most of an atom is empty space. - The positive charge of an atom is concentrated at the centre (the nucleus) and electrons orbit this. - Most of the mass of an atom is in the nucleus.
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4
Q

Limitations of Rutherford’s model

A

The model was unable to show anything about the arrangement of electrons in the orbit.

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5
Q

Continuum Spectrum

A

A spectrum created from a light source producing photons of all wavelengths (and frequencies).

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6
Q

Emission Line Spectrum

A

Light is shone through hot gas (the element being studied), passed through a slit and then a prism. Electrons in the atoms will emit photons with the exact amount of energy to drop energy levels. So only photons of specific wavelengths (and frequencies) are emitted. This produces thin lines of colour in an otherwise spectrum of black.

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7
Q

Absorption Line Spectrum

A

Light is shone through a cold gas, passed through a slit and then a prism. Electrons in the atoms will absorb photons with the exact amount of energy required to jump energy levels. So only photons of specific wavelengths (and frequencies) are absorbed. This produces thin lines of black in an otherwise full spectrum of colour.

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8
Q

What is radioactive decay?

A

The nuclei of some elements are unstable bc of the wrong balance of protons and neutrons. Over time, these nuclei will spontaneously decay by emitting particles and energy. So they transform into the nuclei of another element.

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9
Q

How can electrons move to higher or lower energy levels? (physical processes)

A

To move to a higher energy level:- The gas is heated- Or a photon is absorbedTo move to a lower energy level:- The gas is cooled- Or a photon is emitted

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10
Q

Half-life

A

The time taken for half of the nuclei in a sample to decay (or the activity to fall to 50%).

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11
Q

Natural sources of background radiation

A
  • Cosmic- Terrestrial (eg. radioactive rocks/soil)- Internal (eg. living organisms that have consumed radioactive substances in the food chain)
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12
Q

Artificial sources of background radiation

A
  • Medical (eg. x-rays, radiation treatment)- Industrial/occupational- Nuclear fall out
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13
Q

Define transmutation

A

When nuclei are changed from one element to another by the addition of nucleons. Can occur naturally or artificially in nuclear fusion and nuclear fission.

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14
Q

Nuclear fission

A

The splitting of large nuclei into smaller nuclei by being bombarded by particles like neutrons or alpha particles. Occurs artificially in nuclear power stations.

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15
Q

Nuclear fusion

A

The joining of two nuclei to form a larger nuclei. Only occurs if temperature and pressure is high enough to give them the energy to overcome the electrostatic repulsion between them. It occurs naturally in stars, and is very hard to do artificially. Yields more energy than nuclear fission.

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16
Q

Why do both nuclear fission and nuclear fusion release large amounts of energy?

A

Because during these reactions mass is destroyed and converted to energy.

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17
Q

J to eVeV to MeVMeV to GeV

A

divide by 1.6 x 10^-19divide by 10^6divide by 1000

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18
Q

Define the unified atomic mass

A

The mass of 1/12th of a 12C atom.

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19
Q

Define the mass defect

A

The difference in mass between the individual nucleons and their total mass when bound in the nucleus.

20
Q

Define the binding energy

A

The amount of energy required to break apart a nucleus into separate nucleons.

21
Q

Give the formula for bepn (binding energy per nucleon)

A

bepn = total binding energy of the nucleus/number of nucleons (protons + neutrons)

22
Q

The larger the nucleus . . . (binding energy)

A

the greater its binding energy hence also stability.

23
Q

Give the formula for working out the mass lost in a reaction

A

mass(reactants) - mass(products)

24
Q

Define elementary/fundamental particles

A

No internal structure (are not made up of smaller particles).

25
Q

What are the three types of elementary particles?

A

Leptons (electron family)QuarksExchange particles - gauge bosons

26
Q

Define mesons

A

A hadron. Quark - antiquark pairs. Short-lived as annihilate quickly.

27
Q

Define baryons

A

A hadron. Three quarks or three antiquarks.

28
Q

Why do quarks never exist individually?

A

Because if two quarks are moved apart energy is required. This energy is converted to mass and produces a new quark.

29
Q

What are protons and neutrons made up of?

A

Proton - uud (two up quarks, one down quark)Neutron - udd (one up quark, two down quarks)

30
Q

Gluons

A

Exchange particle for strong interactions.Exchanged between quarks (ONLY!) to hold them together (to form protons and neutrons). Also within hadrons (mesons/baryons).AS PROTONS AND NEUTRONS ARE MADE UP OF QUARKS!!!

31
Q

Pions

A

Also called pi mesons (π). Exchange particles for strong interactions. Made up of a quark and antiquark.Exchanged between hadrons.

32
Q

W and Z bosons

A

Exchange particles for weak interactions.ONLY WITH LEPTONS. Transfer charges between particles.

33
Q

What must be conserved for an interaction to be viable?

A

ChargeLepton numberBaryon numberMass-energyMomentumStrangeness is only conserved in strong interactions (w quarks)! Not conserved in weak interactions (w leptons!)

34
Q

What particles are involved in weak interactions?

A

Leptons. Exchange particles are W and Z bosons.

35
Q

What particles are involved in strong interactions?

A

Quarks ONLY. Gluons are the exchange particles.

36
Q

nm —> m

A

÷ 10-9

37
Q

Define isotope

A

Different nuclei of an element that have different number of neutrons but the same number of protons.

38
Q

What are the four fundamental forces in nature?

A
  • Gravitational force.All particles. Relative strength = 1. Weak force but it is always attractive and has an infinite range. It is dominant over large distances. - Weak nuclear force (weak interaction).Quarks and leptons. Relative strength = 10²⁴. Short range 10⁻¹⁸m. - Electromagnetic force.All charged particles. Relative strength = 10³⁵. It can be attractive or repulsive, has an infinite range and is stronger at short distances (holds atoms and molecules together).- Strong nuclear force (strong interaction).Quarks. Relative strength = 10³⁷. It is very strong but it has a short range. It is attractive at 10⁻¹⁵m and repulsive at smaller distances.
39
Q

What is Coulomb interaction (electrostatic force)?

A

The repulsion between protons.

40
Q

Define nuclide.

A

A particular form of a nucleus.

41
Q

What is unique about the Higgs boson?

A

It is a relatively massive boson and a great deal of energy is required to produce it.

42
Q

Define the Standard Model.

A

The theory that describes the electromagnetic, weak and strong interactions of particles.

43
Q

What is significant about the Higgs boson?

A

It is responsible for the mass of particles in The Standard Model. Without it The Standard Model would no longer be a valid theory.

44
Q

What is the shape of the graph of binding energy per nucleon against nucleon number?

A

A slight curve. There is a peak at 56. This is the hardest nucleus to break apart (it is very stable)!

45
Q

What are exchange particles?

A

Exchange particles are virtual particles which help to meditate force between interacting particles.