Nuclear Chemistry

Front 1

At what point will atomic elements start to undergo radioactive decay

Back 1

generally above with a Z greater than or equal to Po (84)

Front 2

From what point are atomic elements considered artificial (not naturally occurring)

Back 2

at Z greater than 92

Front 3

nuclear stability ratio in smaller nuclei

Back 3

stability achieved when (A-Z)/Z is 1

Front 4

nuclear stability for larger nuclei

Back 4

(A-Z)/Z is greater than 1 (1.2-1.4), need greater number of protons

Front 5

which element has the most stable isotopes

Back 5

Tin (Sn) with 10 stable isotopes

Front 6

2 points of view from which to consider nuclear stability

Back 6

thermodynamic (PE of a particular nucleus as compared with PE sum of its component protons and neutrons) and kinetic (proba that nucleus will undergo radioactive decay)

Front 7

what combinations of protons and neutrons seem to confer special stability

Back 7

nuclides with even numbers of protons and neutrons (more stable than odd counterparts), magic numbers (2,8, 20,28,50,82,126) patterns similar to atoms (noble gases)

Front 8

beta particle

Back 8

represents an electron, neg. charge and no mass, emitted during nuclear decay, but does not exist inside nucleus, is a product of reaction (a given quantity of energy can become a particle under certain circumstances)

Front 9

beta particle production

Back 9

occurs in smaller nuclei, as mass number stays same, neutron/proton ratio decreases (only reaction where this occurs)

Front 10

what is the net effect of beta particle production

Back 10

to change a neutron to a proton (therefore expect nuclides that lie above zone of stability (more neutrons than protons) to be beta particle producers

Front 11

gamma ray

Back 11

refers to high-energy photon, freq. accompany nuclear decays and particle reactions, 2 gamma rays of diff. E are produced with an alpha particle

Front 12

how can a nucleus with excess E relax to its ground state

Back 12

emitting a gamma ray (pure energy)

Front 13

positron production

Back 13

occurs for nuclides below zone of stability (few neutrons compared to protons), its net effect is to raise the neutron proton ratio by changing proton to neutron (emit +1)

Front 14

positron

Back 14

particle with same mass (0) of electron, but opposite charge

Front 15

annihilation

Back 15

when particle (beta particle) and antiparticle (positron) collide, the particulate matter is changed to electromagnetic radiation in form of gamma ray (high E photon)

Front 16

electron capture

Back 16

process in which one of inner-orbital electrons is captured by nucleus, results in 1 less proton (higher neutron/proton ration), might have interested alchemists if faster rate

Front 17

rate of decay

Back 17

negative in the change in the number of nuclides per unit time (-ΔN over Δt), directly proportional to number of nuclides in a given sample (neg. bc nuclides decreasing)

Front 18

danger of Sr-90

Back 18

Sr-90 is absorbed in grass, hay, and passed to humans through cow's milk, lodges in bones and bc of long half life (28.8yrs) causes radiation damage that may lead to cancer

Front 19

another possibility of nuclear decay besides beta and alpha particle production

Back 19

nuclear fission (splitting of heavy nuclei into smaller nuclides) and fusion (joining lighter nuclides into a heavier nuclei)

Front 20

alpha particle

Back 20

similar to He nucleus (4 mass, 2 protons)

Front 21

alpha decay

Back 21

results in ejection of positive particles, typically occurs in heavier nuclei

Front 22

radiotracers and radiolabels

Back 22

used to measure the speed of chemical processes and to track the movement of a substance through a natural system such as a cell or tissue

Front 23

E=mc2

Back 23

demonstrates a possible conversion btwn E and mass, for a small change in mass (mass defect), there is a corresponding change in E (binding E)

Front 24

binding energy

Back 24

represents how much E is needed to break down a nucleus into its components (nucleons)

Front 25

binding E trends for nucleus vs. nucleons

Back 25

total binding energy for nucleus is higher the greater the atomic number, but if you look at binding E per nucleon, trends are diff. (56-Fe is upper limit, most stable)

Front 26

decay series

Back 26

successive radioactive processes until a stable nucleus is achieved, usually a combo of alpha and beta decays

Front 27

abundance and rates of reaction

Back 27

diamond is more stable than graphite, but graphite is more abundant because its rate of reaction is faster

Front 28

first order nuclear processes

Back 28

all nuclear processes are first order processes, meaning the rate of reaction is directly proportional to the concentration of the reactant

Front 29

nuclear transmutation

Back 29

conversion of one chemical element or isotope into another. This occurs either through nuclear reactions (in which an outside particle reacts with a nucleus), or through radioactive decay (where no outside particle is needed)

Front 30

nuclear fission

Back 30

releases a tremendous amount of energy, typically initiated by neutron, (NB for every neutron used, 3 neutrons are produced, leads to supercritical situation if uncontrolled)

Front 31

chain reaction

Back 31

a self-sustaining process

Front 32

subcritical

Back 32

process dies out (less than 1 neutron causes another fission event)

Front 33

critical

Back 33

process sustains itself at an even level (exactly 1 neutron from each fission event causes another fission event)

Front 34

supercritical

Back 34

process escalates rapidly (if more than 1 neutron from each fission event goes on to cause another fission event)

Front 35

critical mass

Back 35

amount of substance that allows a critical reaction

Front 36

geometric series

Back 36

describes progression of nuclear fission reactions, (number of neutrons released increases in geometric progression)

Front 37

how many neutrons are produced for every neutron used in a nuclear fission reaction

Back 37

3 neutrons for every 1 neutron used (need a material to absorb other 2 neutrons produced)

Front 38

nuclear fusion

Back 38

occurs on sun, believed to be primary source of helium on earth, cannot be replicated because required extremely high temps (4x10 to the 7 K)

Front 39

What does E=mc2 show

Back 39

that there is a possible conversion btwn energy and mass