Complex Chemistry/ Nuclear Chemistry

Question 1

Radiation

Answer 1

Emission of subatomic particles or high energy electromagnetic radiation

Question 2

Nuclear Decay

Answer 2

Integration in the nucleus. Continuous, spontaneous random process

Question 3

Radioisotope/ radio nuclide

Answer 3

A nucleus that changes its structure spontaneously and continuously while emitting characteristics types of ration

Question 4

3 types of emissions

Answer 4

Alpha/ Beta/ Gamma

Question 5

Alpha emission

Answer 5

• Short range, highest ionization.
• Stopped by thin card, cannot penetrate skin, causes severe burn
• A decrease by 4, Z decrease by 2

Question 6

Beta emission – 3 types:

Answer 6

Negatron Decay / Positron Decay/ Electron Capture

- Penetrate further than alpha, stopped by metal

Question 7

Negatron Decay

Answer 7

• Emission of high speed, energetic e- or negatively charged beta particles
• Neutron to proton transition n > p + (-1e) + v (v = antineutrino)
• Z decrease by 1, A stay the same

Question 8

Positron Decay

Answer 8

• emission of high energetic positively charged electrons (beta particles, antiparticle)
• Proton to neutron transition p > n + (+1e) + v (v = neutrino)
  (Antiparticle meets corresponding particle = annihilation)
• +1e + -1e > 2 gamma distinctive energy of 0.51 MeV
• Z decrease by 1, A stays the same

Question 9

Electron Capture

Answer 9

• Proton to neutron transition p + (-1e) > n + x-rays

- Z decreases by 1, A remains the same

Question 10

Gamma radiation

Answer 10

• Short wavelength, high energy electromagnetic radiation
• Very penetrating; stopped by thick lead plate or concrete shielding
• Emission of alpha and beta normally results in an excited state nuclide. Transition from excited state to ground state results in emission of gamma radiation

Question 11

Nuclide

Answer 11

An atom of a particular isotope

Question 12

Radioactive decay

Answer 12

Parent nuclide > daughter nuclide + nuclear radiation
Ratio of p+ & n0 change in parent nuclide > new elements formed
(p+ gives identity; e- gives personality)

Question 13

Radioactivity

Answer 13

Unstable atom nuclei is spontaneously integrating and simultaneously giving out nuclear radiation

Question 14

Chemical reaction vs Nuclear reaction

Answer 14

• Atoms are re- arranged to form new molecules in CR
• Different isotopes of the same element undergo same CR
• Different isotopes of the same element DO NOT all undergo the same NR
• Atoms are destroyed or created in NR
• Atomic mass change in NR
• Energy changes much greater in NR (E=mc^2)

Question 15

Nuclear stability

Answer 15

Base on n:p ratio

Question 16

Z < 20

Answer 16

stable ratio normally 1:1

Question 17

Z > 20

Answer 17

1:1 to 1:1.5 is normally stable range

Question 18

A > 209

Answer 18

major instability

Question 19

Z > 83

Answer 19

instability

Question 20

A > 238,

Answer 20

spontaneous fission

Question 21

• Beta emission more likely for ______elements

- Alpha emission more likely for ______elements

Answer 21

Beta: lighter

Alpha: heavier

Question 22

• Few nuclides with Z < 60 will emit _________

Answer 22

alpha particles

Question 23

• Elements with_______Z number most abundant

- the only one of the 8 most abundant elements with odd Z number ?

Answer 23

an even Z number

Al

Question 24

Nuclear Fission

Answer 24

the process of splitting the atoms

Question 25

Nuclear Fusion

Answer 25

a nuclear reaction in which two or more atomic nuclei collide at very high speed and join to form a new type of atomic nucleus

Question 26

Radioactivity half life equation

Answer 26

T(1/2) = 0.6931/ λ

Question 27

Half - life

Answer 27

the time taken for half of the radioactive nuclei to decay.

Question 28

Radioisotopes

Answer 28

Isotopes that are radioactive

Question 29

Becquerel

Answer 29

- the activity of a quantity of radioactive material in which one nucleus decays per second - 1 disintegration per second SI unit= 1 Bq

Question 30

Activity =

Answer 30

- 1 Curie unit (Ci) | - the activity of 1g of pure (226) Ra= 3.7 x 10^10 Bq

Question 31

Specific activity

Answer 31

activity per unit mass

Question 32

Dosage is _____

Answer 32

2mSv per year - 20% own bodies, 30% cosmic/ space, 40% Radon, 10% medical exposure

Question 33

Absorbed dose

Answer 33

amount of energy SI unit Gray (Gy). 1 Gy = 1JKg^-1

Question 34

Rad

Answer 34

old unit of Gy for absorbed dose | 1 Gy= 10 Rad

Question 35

Dose equivalent measured in

Answer 35

Sieverts (Sv) Old unit was Rem 1Sv = 100 Rem

Question 36

Sv =

Answer 36

Gy x Q factors

Question 37

Q factors

Answer 37

Biological effectiveness and must take into account type of radiation and types of tissues affected Different tissues have different Q factors

Question 38

alpha radiation has Q factor of _______

Answer 38

x 20 greater than either beta or gamma radiation

Question 39

3 methods of detection & measurement of radioactivity in the environment

Answer 39

~ Geiger- Muller tube - ionisation of gases ~ Scintillation Techniques - excitation of liquids or solids ~ Dosimeters - induction of chemical change

Question 40

Activity

Answer 40

no of nuclear disintegrations per sec (1 Becquerel= 1 disintegration/ second)

Question 41

2 types of Radioactivity measurement

Answer 41

Differential - individual emissions per unit time - quantitative analytical work Integral - total cumulative effect - dosimetry

Question 42

For consistent radioactivity measuring results,_______

Answer 42

- background needs to be measured - Significant number of measurements to be made - due to random nature of process of decay - Statistical assessment of results required

Question 43

Counting Efficiency (E)

Answer 43

Observed counts from detector/ activity from source

Question 44

Factors affect E (__________)

Answer 44

Counting efficiency - Geometrical position of counter wrt to source - Absorption of radiation by any material between source and detector - Limitations of detector - Dead time losses

Question 45

Measurements of Environmental Radioactivity

Answer 45

Measurement of radioactivity in water, air, many foods and animals done routinely

Question 46

3 Environmental Radioactivity measuring method

Answer 46

Radiotracer methods Activation Methods Isotope Dilution Methods

Question 47

Medical application techniques

Answer 47

- Positron emission tomography - Single photon emission computed tomography (SPECT) - Cardiovascular imaging

Question 48

Nuclear medicine imaging is useful for detecting

Answer 48

- Tumors - Blood cell disorders - Inadequate functioning of organs