Nucleus and Radiation

Question 1

What is the nucleus composed of?

Answer 1

Protons and neutrons

Question 2

What do each chemical element have?

Answer 2

Given atomic number (no. of protons)

Question 3

Define Isotope

Answer 3

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

Question 4

What are 3 naturally occurring isotopes?

Answer 4

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

Question 5

What do different isotopes have?

Answer 5

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

Question 6

How do you convert amu –> kg?

Answer 6

1amu = 1.6605x10^-27

Question 7

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

Answer 7

Strong nuclear force

Question 8

What are the 4 fundamental forces of nature?

Answer 8

1. Gravitational
2. Electromagnetic
3. Strong nuclear
4. Weak nuclear

Question 9

What are the properties of Gravitational?

Answer 9

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

Question 10

What are the properties of Electromagnetic?

Answer 10

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

Question 11

What are the properties of Strong Nuclear?

Answer 11

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

Question 12

What are the properties of weak nuclear?

Answer 12

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

Question 13

How does the strong nuclear force overcome repulsion?

Answer 13

Between positively charged protons to hold nucleus together

Question 14

The binding energy

Answer 14

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

Question 15

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

Answer 15

Experimentally

When nucleus is formed from protons and neutrons

Question 16

Define mass defect

Answer 16

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

Question 17

What is mass defect due to?

Answer 17

Equivalence of mass and energy

Question 18

What equation brings together the binding energy and mass defect?

Answer 18

E=mc^2

Question 19

What is binding energy?

Answer 19

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

Question 20

What is a measure of stability of nucleus?

Answer 20

Binding energy per nucleon

Question 21

How can a light nuclei become more stable?

Answer 21

Fusing together to form a heavier nuclei

Question 22

How can a heavy nuclei become more stable?

Answer 22

By splitting (fission) to form a light nuclei

Question 23

What is 1eV?

Answer 23

1.6x10^-19

Question 24

What is the speed of light?

Answer 24

3x10^8ms-1

Question 25

What are alpha particles emitted by?

Answer 25

Radioactive nuclei | alpha decay

Question 26

What is the charge of alpha particle

Answer 26

2+

Question 27

What has the same composition as a helium nucleus?

Answer 27

alpha particles

Question 28

What are conserved?

Answer 28

Nucleons and charges

Question 29

How are alpha decay written symbollically?

Answer 29

A Z X ---> A-4 , Z-2 Y + 4,2He The mass number A is reduced by 4 and proton 2

Question 30

What do alpha particles have?

Answer 30

short range in air (<10cm)

Question 31

What is the consequence of alpha radiation outside the body?

Answer 31

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

Question 32

What is the consequence of alpha radiation inside the body?

Answer 32

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

Question 33

What can alpha particles ionize?

Answer 33

Atoms and molecules with which they collide | i.e. knock electrons out of orbitals leaving a charged ion

Question 34

How can ions cause damage to living tissue?

Answer 34

They can break chemical bond and produce damaging free radicals

Question 35

What are the two types of beta decay?

Answer 35

B- and B+

Question 36

What is B- decay?

Answer 36

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

Question 37

How can B- decay be written as symbollically?

Answer 37

A,Z X --> A, Z+1 Y + e- + Ve

Question 38

What is B+ decay?

Answer 38

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

Question 39

How can B+ decay be written as symbollically?

Answer 39

A, Z X --> A, Z-1 Y + e+ + Ve

Question 40

What are called beta particles?

Answer 40

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

Question 41

What range do Beta particles have?

Answer 41

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

Question 42

What are less densely ionizing than alpha particles?

Answer 42

Beta particles

Question 43

What are gamma radiation?

Answer 43

High energy (high frequency) photons of electromagnetic radiation

Question 44

How are gamma radiation produced?

Answer 44

By product of Alpha/Beta decay

Question 45

What happens when a nucleus emits a beta particle?

Answer 45

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

Question 46

Where is 99mTc extensively used in?

Answer 46

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

Question 47

How can gamma radiation be stopped?

Answer 47

Very energetic | Thick sheet of lead or several metres of concrete

Question 48

What can gamma radiation cause?

Answer 48

Ionization | lower probability than alpha or beta particles

Question 49

what is PET?

Answer 49

Imaging technique based on B+ decay and Gamma radiation

Question 50

What is electron mass?

Answer 50

9.11 x 10^-31

Question 51

How do you conserve momentum of gamma radiation?

Answer 51

Two gamma ray photons must travel in opposite directions

Question 52

What is momentum of photon given by?

Answer 52

p=h/wavelength

Question 53

What is mode of decay of a nucleus dependent on?

Answer 53

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