Nuclear and environmental chemistry

Question 1

When did french scientists Pierre and Maire Curie discover the radioactive elements?

Answer 1

1898

Question 2

When did french physicist henri becquerel discover radioactivity in uranium?

Answer 2

1986

Question 3

What are stable isotopes

Answer 3

atoms of elements can have multiple isotopes with different numbers of neutrons in the nucleus

Question 4

What does radioactive isotopes mean?

Answer 4

isotopes have an unstable nucleus - occurs when the nucleus of an atom has an excess of protons or neutrons

the emit particles/radiation to regain stability

Question 5

What does radioactivity refer to?

Answer 5

to unstable atomic nuclei which spontaneously disintegrate and simultaneously emit nuclear radiation

Question 6

What does the term disintegration refer to?

Answer 6

one nuclide (atom) changing into another nuclide

Question 7

What does the term nuclear radiation refer to?

Answer 7

the emitted particles or high frequency light

Question 8

What are 3 types of nuclear radiations?

Answer 8

alpha particle - when a radioactive isotope releases decay. A helium nuclei. 4 protons and 2 neutrons.

Beta particle - negatively charged electron

Gamma rays - photon (short wavelength)

Question 9

Decay series

Answer 9

some radionuclides need to undergo a series of disintegrations before reach a stable nuclide

This can involve several different radionuclides and types of nuclear radiation emitted

Question 10

How is radioactive detected?

Answer 10

a geiger-mueller counter

Question 11

What is the SU unit called?

Answer 11

becquerel - defined number of disintegrations it undergoes

The activity of radioisotope is proportional to the number of radioactive nuclei

Question 12

Radioactive decay - what does half-life refer to?

Answer 12

processes are first order kinetic process

Half life refers to the time required for half the original sample of nuclei to decay

Question 13

What is the term transmutations? and how is this achieved?

Answer 13

refers to the conversion of one
type of element to another type following particle bombardment

naturally occuring and can physically change it with;
- Accelerators
- Cyclotrons
- Nuclear reactors

Question 14

What is the main principle radiometric dating?

Answer 14

radionuclides undergo disintegration at a constant rate, which differs between each radionuclide

carbon-14 for radiometric dating on shorter timescales

Naturally occuring carbon - 3 isotopes
12C - 98.93%
C13 - 1.07%
C14 - 0.00000001%

reliable detection of radioisotopes occurs up to ten half-lives

Question 15

How is carbon-14 incorporated into radiocarbon dating?

Answer 15

nitrogen is atmosphere collides with cosmic rays, transmute nitrogen into carbon 14 isotope - continuous production. When that transmutation occurs, that C14 atom then taken up by plants - animals eat the pants. consistent ratio consumed into molecules. Once created - starts to decay.

when animals dies, the carbon 14 begins to decay, this ratio with change relative to the ration.

Question 16

What is isotopic dilution? and what are the 3x assumptions made in regards to this?

Answer 16

Way to assess amount of in a poll in a large pool - take a sub sample, mark it, return capture, dilutions occurs, period of time later, resample, and calculate marked individuals.

1. assumptions associated with this; the chance of capturing unmarked and marked individuals must be equal
2. the proportion of unmarked to marked individuals remains constant
3. Population size does not increase or decrease

estimating blood volume
soil phosphorus kinetics
Counting fish in a large pool
Tracer - giving a unique fingerprint

Question 17

What issues occur for labeling/tracer?

Answer 17

if added to soil - if taken up by animals. Radioactive substance inside of animals now.

Question 18

How is radioactivity found in the environment? and what are four factors to consider?

Answer 18

Found in the environment
1. the energy of radiation
2. the penetrating ability of radiation
3. the ionising ability of the radiation
4. the chemical properties of radiation source

Question 19

How does ionising radiation cause damage?

Answer 19

Produces a free radical that can damage your DNA - small scale you body has mechanisms to repair it. however, larger amounts/ higher concentrations, your body can’t handle the amount.

Question 20

What are 3 photochemical reactions?

Answer 20

1. photodissociation - refers to the rutpure of a chemical bind following the absorption of a photon - the minimum energy required to break the bond between two oxygen atoms is equal to the bond energy

Calculations - review.

2. photoionisation - refers to a molecule absorbing energy resulting in an electron being rejected - ionisation energy.
3. Ozone in the atmosphere in stratosphere

compound absorbing photons with wavelengths from240 - 310nm

continuous formation and decomposition (cycle - releasing heat)

Question 21

how can the ozone layer be affected?

Answer 21

1. natural events - volcanic eruption, affects the processes and raise temperature
2. production of CFCs - trying to remove CFCS found in fridge AC aerosols etc. Photodissociation of CFCs - releases cholrine, binds with ozone - creating high energy radiation (breaks down ozone)

Question 22

What are 4 anthropogenic events?

Answer 22

1. heavy metals (Cd, Pb and Hg)
2. detergents and fertilisers
3. acid water
4. Pharmaceuticals