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P1 Introductory science and methods > Nucleus and Radiation > Flashcards

Nucleus and Radiation Flashcards

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1
Q

What is the nucleus composed of?

A

Protons and neutrons

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2
Q

What do each chemical element have?

A

Given atomic number (no. of protons)

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3
Q

Define Isotope

A

Atoms with the same number of protons but a different number of neutrons

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4
Q

What are 3 naturally occurring isotopes?

A

12-6C
13-6C
14-6C

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5
Q

What do different isotopes have?

A

Different probabilities of being found naturally (e.g. they have a different natural abundance)
C-12 = 98.93
C-13 = 1.109
C-14 = 1 part per trillion

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6
Q

How do you convert amu –> kg?

A

1amu = 1.6605x10^-27

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7
Q

?What are the particles in the nucleus held together by?

A

Strong nuclear force

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8
Q

What are the 4 fundamental forces of nature?

A
  1. Gravitational
  2. Electromagnetic
  3. Strong nuclear
  4. Weak nuclear
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9
Q

What are the properties of Gravitational?

A

Range: Infinite
Act between: All masses
Effect: Holds stars and planets in orbit
Relative magnitude: 10^-36

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10
Q

What are the properties of Electromagnetic?

A

Range: Infinite
Act between: All charge
Effect: Holds atom together
Relative magnitude: 1

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11
Q

What are the properties of Strong Nuclear?

A

Range: Within nucleus
Act between: Nucleons
Effect: Hold nuclei together
Relative magnitude:1

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12
Q

What are the properties of weak nuclear?

A

Range: within nucleus
Act between: Nucleons and electrons
Effect: Responsible for radioactivity
Relative magnitude: 0.01

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13
Q

How does the strong nuclear force overcome repulsion?

A

Between positively charged protons to hold nucleus together

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14
Q

The binding energy

A
  1. Energy radiated away when protons and neutrons are brought together to form the nucleus
  2. Energy required to overcome strong nuclear force and break apart nucleus
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15
Q

When is mass of nucleus < sum of masses of protons and neutrons observed?

A

Experimentally

When nucleus is formed from protons and neutrons

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16
Q

Define mass defect

A

the difference between the mass of an isotope and its mass number, representing binding energy.

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17
Q

What is mass defect due to?

A

Equivalence of mass and energy

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18
Q

What equation brings together the binding energy and mass defect?

A

E=mc^2

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19
Q

What is binding energy?

A

the energy that holds a nucleus together. This is equal to the mass defect of the nucleus.

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20
Q

What is a measure of stability of nucleus?

A

Binding energy per nucleon

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21
Q

How can a light nuclei become more stable?

A

Fusing together to form a heavier nuclei

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22
Q

How can a heavy nuclei become more stable?

A

By splitting (fission) to form a light nuclei

23
Q

What is 1eV?

A

1.6x10^-19

24
Q

What is the speed of light?

A

3x10^8ms-1

25
Q

What are alpha particles emitted by?

A

Radioactive nuclei

alpha decay

26
Q

What is the charge of alpha particle

A

2+

27
Q

What has the same composition as a helium nucleus?

A

alpha particles

28
Q

What are conserved?

A

Nucleons and charges

29
Q

How are alpha decay written symbollically?

A

A Z X —> A-4 , Z-2 Y + 4,2He

The mass number A is reduced by 4 and proton 2

30
Q

What do alpha particles have?

A

short range in air (<10cm)

31
Q

What is the consequence of alpha radiation outside the body?

A

Less hazardous as they would be stopped by outer layers of skin

32
Q

What is the consequence of alpha radiation inside the body?

A

Very hazardous

All energy would be deposited in small volume of living tissue e.g. lungs

33
Q

What can alpha particles ionize?

A

Atoms and molecules with which they collide

i.e. knock electrons out of orbitals leaving a charged ion

34
Q

How can ions cause damage to living tissue?

A

They can break chemical bond and produce damaging free radicals

35
Q

What are the two types of beta decay?

A

B- and B+

36
Q

What is B- decay?

A

A neutron in the nucleus decays to a proton, an electron and an electron antineutrino

37
Q

How can B- decay be written as symbollically?

A

A,Z X –> A, Z+1 Y + e- + Ve

38
Q

What is B+ decay?

A

A proton in the nucleus decays to a neutron, a positron and electron neutrino

39
Q

How can B+ decay be written as symbollically?

A

A, Z X –> A, Z-1 Y + e+ + Ve

40
Q

What are called beta particles?

A

Both electrons (e-) and positrons (e+)

41
Q

What range do Beta particles have?

A

several metres in air but can be stopped by a sheet of aluminium

42
Q

What are less densely ionizing than alpha particles?

A

Beta particles

43
Q

What are gamma radiation?

A

High energy (high frequency) photons of electromagnetic radiation

44
Q

How are gamma radiation produced?

A

By product of Alpha/Beta decay

45
Q

What happens when a nucleus emits a beta particle?

A

It will be in an excited state. It can return to its ground state by emitting a gamma ray

46
Q

Where is 99mTc extensively used in?

A

Nuclear medicine e.g. to perform bone scans to look for metastases

47
Q

How can gamma radiation be stopped?

A

Very energetic

Thick sheet of lead or several metres of concrete

48
Q

What can gamma radiation cause?

A

Ionization

lower probability than alpha or beta particles

49
Q

what is PET?

A

Imaging technique based on B+ decay and Gamma radiation

50
Q

What is electron mass?

A

9.11 x 10^-31

51
Q

How do you conserve momentum of gamma radiation?

A

Two gamma ray photons must travel in opposite directions

52
Q

What is momentum of photon given by?

A

p=h/wavelength

53
Q

What is mode of decay of a nucleus dependent on?

A

Relative number of protons and neutrons
Proton rich nuclei tend to decay via b+ decay
Neutron rich nuclei tend to decay via b- decay
Heavy nuclei tend to decay via alpha decay

P1 Introductory science and methods (14 decks)

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