WEEK 13 (Nuclear Physics)

Question 1

What is atomic number?

Answer 1

The number of protons in the nucleus

Question 2

What is Neutron number?

Answer 2

The number of neutrons in the nucleus

Question 3

What is Mass number?

Answer 3

The number of protons and neutrons in the nucleus
(Protons + Neutrons = Atomic number)

Question 4

What is atomic mass measured in?

Answer 4

Atomic mass is measured in atomic mass units and is equal to 1/12 the mass of a Carbon-12 atom

Question 5

What are the charges of Electrons, Protons and Neutrons?

Answer 5

Electrons = Negative
Protons = Positive
Neutron = Neutral

Question 6

The stability of the nucleus depends on which numbers

Answer 6

Z (Atomic) & N (Neutron) Numbers

Question 7

Describe the Forces within the nucleus

Answer 7

Protons mutually repel each other due to Coulomb’s repulsive forces between protons however due to the attractive “nuclear force” between the nucleons, the force keeps the nucleus together.

Question 8

Describe the Nuclear force

Answer 8

• Very strong
• Al­lows it to dom­i­nate elec­tro­mag­netic forces like the re­pul­sive Coulomb force in sta­ble nu­clei
• Very short distance

Question 9

What are the three types of radioactivity?

Answer 9

α – helium nucleus
β – electrons or positrons
γ – high energy photons

Question 10

What is the history behind Radioactivity?

Answer 10

• In 1896 Henry Becquerel discovered that uranium salt crystals emit an unknown radiation that darkens photographic plate
• Marie and Pierre Curies discovered Polonium and Radium

Question 11

What is the “Half-life”?

Answer 11

The time it takes to halve the number of radioactive nuclei

Question 12

Describe Nuclear binding energy

Answer 12

Mass of nucleus is less than total mass of its individual protons end neutrons, thus mass energy of nucleus is less than total mass energy of protons and neutrons

Question 13

Explain why Radiation is dangerous for living organisms

Answer 13

Interaction of nuclear radiation with matter leads to ionisation thus why UV and X-RAYS are dangerous for living organisms

Question 14

What are Isotopes used for in Nuclear medicine?

Answer 14

Radiolabelling

Question 15

What are the properties of Gamma rays?

Answer 15

• Shortest wavelength
• Highest frequencies emitted by radioactive nuclei
• Highly penetrating
• Cause serious damage when absorbed by living tissues

Question 16

Describe the method of how radioisotopes are used in medicine

Answer 16

1) A radioisotope is injected into the bloodstream; the radioisotope is usually a simple soluble dissolved ion
2) A marker radioisotope is attached to a specific ligand to create a radio ligand whose properties bind it to certain types of tissues
3) The ligand and radioisotope is carried and bound to a specific organ of interest in the body where emitted gamma photons are detected by gamma camera

Question 17

What do SPECT and PET scanners have in common?

Answer 17

Both of them give time dependent 3D images of location of radioisotopes

Question 18

What is the disadvantage of a PET scanner?

Answer 18

• High initial cost
• Ongoing operating costs

Question 19

What is High spatial resolution used for in medicine?

Answer 19

Clinical oncology for diagnosis of certain diffuse brain diseases and tumours