Ch. 11- Nuclear Chemistry Flashcards
radioactive decay
the disintegration of an unstable atomic nucleus with spontaneous emission of radiation
radioisotopes
atoms or ions with radioactive nuclei
cosmic rays
extremely high-energy radiation from outer space
background radiation
constantly occurring radiation from cosmic rays, and from natural radioactive isotopes in air, water, soil, and rocks
ionizing radiation
radiation that produces ions as it passes through matter; examples= x-rays & nuclear radiation
is our exposure to background radiation harmful?
no, the total amount of background radiation to which the average person is exposed is less than 0.5% of the amount that causes symptoms of radiation sickness
how can high levels of ionizing radiation be harmful?
- damages live tissue (white blood cells are most vulnerable)
- affects bone marrow, causing less red blood cells to be reduced, resulting in anemia
- induces leukemia
- causes mutations in DNA
alpha decay
emission of an alpha particle by a radioactive nucleus
beta decay
emission of a beta particle by a radioactive nucleus
why is beta decay complicated?
in beta decay, a neutron within the nucleus is converted into a proton (which remains in the nucleus) and an electron (which is ejected)
gamma decay
emission of a gamma ray by a radioactive nucleus
biggest difference between gamma decay & alpha/beta decay
different from alpha & beta decay because gamma radiation has no charge and no mass; A (nucleon #) & Z (atomic #) of emitting atom is changed
positron
a positively charged particle with the mass of an electron
positron emission
a type of radioactive decay that can be envisioned by the change of a proton in the nucleus into a neutron & a positron, with the positron being emitted from the nucleus
what is it about positron emission & electron capture that differentiates them from the 3 common types of radioactive decay (alpha/beta/gamma)?
they both result in a decrease of 1 in atomic number, but with no change in nucleon number
what happens after positron emission?
the original nucleus has 1 fewer proton & 1 more neutron than it had before, and the emitted positron quickly encounters an electron where both particles are then annihilated & turned into energy (specifically, 2 gamma rays)
electron capture (EC)
a type of radioactive decay in which a nucleus absorbs an electron from the first or second shell of the atom, causing the electron to combine with a proton to form a neutron
what happens after EC?
eventually an electron from a higher shell drops to the level vacated by the captured electron, which releases an x-ray
half-life
the length of time required for one-half of the radioactive nuclei in a sample to decay
half-life
the length of time required for one-half of the radioactive nuclei in a sample to decay
becquerel (Bq)
a measure of the rate of radioactive decay (isotope’s activity); 1 Bq = 1 disintegration per second
becquerel (Bq)
a measure of the rate of radioactive decay (isotope’s activity); 1 Bq = 1 disintegration per second
carbon-14 dating
a radioisotopic technique for determining the age of artifacts, based on the half-life of carbon-14
carbon-14 dating
a radioisotopic technique for determining the age of artifacts, based on the half-life of carbon-14
which carbon isotopes do we have on Earth & how much of each?
carbon-12 (99%) & carbon-13 (1%)
explain the process in which carbon-14 is formed & concentrated in Earth’s atmosphere & living things
nitrogen is abundant in Earth’s upper atmosphere & cosmic rays are constantly raining down on Earth
- cosmic rays collide with particles in Earth’s atmosphere, emitting high energy neutrons
- emitted neutrons collide with nitrogen atoms, which emits a proton, resulting in formation of carbon-14
- carbon-14 becomes concentrated in CO2 in Earth’s upper atmosphere
- CO2 is then introduced to living things via photosynthesis
what is the half-life of carbon-14?
5730 years
how old must an object be for carbon-14 dating to be accurate?
100-50,000 years old
transmutation
the conversion of one element into another
tracers
radioisotopes used to trace the movement of substances or locate the sites of activity in physical, chemical, and biological systems
what do tracers allow us to do?
- detect leaks in underground pipes
- measure the thickness of sheet material during production
- determine frictional wear in piston rings
- determine the uptake of phosphorus and its distribution in plants
why do we use radioisotopes to induce mutations?
- exposing seeds or other parts of plants to neutrons or gamma rays increases the likelihood of genetic mutations
- saves plant populations & improves varieties
- can render insect populations sterile
- kills insect populations & limits need for pesticides
- irradiate food as a method of preservation
- radiation destroys microorganisms & enzymes that cause food to spoil
what can block an alpha particle?
- a sheet of paper
- outer layer of skin
what can block a beta particle?
- a sheet of aluminum
- plexiglass
what can block a gamma ray?
- a meter of concrete
- several cm of lead
is the mass of the starting material the same amount as the mass of the product in chemical reactions that give off heat?
no, the starting material loses a small amount of mass when heat is given off, but it’s too small of an amount to be measurable
mass-energy equation
E=mc2, in which E is energy, m is mass, and c is speed of light
binding energy
energy that holds the nucleons together in an atom’s nucleus
nuclear fusion
the combination of two small atomic nuclei to produce one larger nucleus
Emilio Segrè
(with Enrico Fermi) Italian scientist who conducted an experiment in which Uranium atoms were bombarded with neutrons in an attempt to create elements with higher atomic numbers than Uranium (had the high atomic # at the time)
Otto Hahn & Fritz Strassman
German chemists who repeated Fermi-Segrè experiment & found Barium isotopes among the reaction products
Lise Meiter
Austrian physicist who looked over Hahn’s work & discovered that the uranium nuclei had split apart (nuclear fission)
Otto Frisch
Austrian physicist who coined the name “nuclear fission”
nuclear fission
the splitting of an atomic nucleus into two smaller ones
Enrico Fermi
Italian scientist who conducted Fermi-Segrè experiment, received the 1938 Nobel Prize in Physics, and then fled to the U.S.
chain reaction
a self-sustaining reaction in which one or more products of one event cause one or more new events
Leo Szilard
one of the first scientists to discover chain reaction
what was the importance of the discovery of chain reaction?
chain reaction can be extremely dangerous, and if other countries were to become aware of it (specifically Germany during WWII), they could make explosive bombs; it was critical for the U.S. government to take action on such discovery
which element has the most stable nuclei?
Iron (Fe)
Manhattan Project
a massive, highly secret research project for the study of atomic energy
who launched the Manhattan Project?
President Franklin D. Roosevelt (kept secret from VP Harry Truman)
what were the focuses of Manhattan Project’s 4 separate research teams?
- sustaining a nuclear fission chain reaction
- enriching uranium so that it contained about 90% of the fissionable isotope uranium-235
- making plutonium-239 (another fissionable isotope)
- constructing a bomb based on nuclear fission
which subatomic particle is required for nuclear fission?
neutron
critical mass
a minimum amount of fissionable material required to achieve a self-sustaining chain reaction
natural uranium is made of which isotopes?
99.27% uranium-238 & 0.72% uranium-235
process for enriching uranium with uranium-235
- a separation method was used to convert uranium into gaseous uranium hexafluoride (UF6)
- UF6 was passed through thousands of pinholes
- UF6 molecules containing uranium-235 outdistanced other & became concentrated
depleted uranium
remaining uranium after enrichment process, includes only about 0.2% uranium-235
how was depleted uranium once used?
used in weapons, it could pierce through metal & cause serious health problems (heart & lungs) if inhaled
how is plutonium made?
uranium-238 would decay to form neptunium (Np), which would decay to form plutonium (Pu)
Glenn T. Seaborg
leader of the research team who figured out how to make plutonium (Pu)
Robert Oppenheimer
leader of research team responsible for constructing nuclear bombs
name the sites of the 4 research teams of the Manhattan Project
- Chicago, IL (sustaining fission chain reaction)
- Oak Ridge, TN (enriching uranium)
- Hanford, WA (making plutonium-239)
- Los Alamos, NM (constructing nuclear bomb)
who led the Chicago, IL team of the Manhattan Project?
Enrico Fermi
which 2 models of atomic bombs were developed?
- based on uranium-235
- 2. based on plutonium-239
how did the uranium-235 atomic bomb work?
bomb contained pieces of uranium-235 of subcritical mass plus a neutron source to initiate the fission reaction; when all pieces are forced together using a high explosive, nuclear chain reaction is triggered
where were the 3 US atomic bombs dropped?
- 1st bomb was plutonium & was dropped in Alamogordo, NM as a test
- 2nd bomb “Little Boy” was uranium & was dropped in Hiroshima on 8/6/45, causing over 100,000 deaths
- 3rd bomb “Fat Man” was plutonium & was dropped in Nagasaki
how did WWII end?
“Little Boy” and “Fat Man” resulted in Japan surrendering on 8/14/45 & WWII ending
radioactive fallout
radioactive debris produced by explosion of a nuclear bomb
what are the 3 most concerning isotopes in radioactive fallout & what are their half-lives?
- Strontium-90 (acts as calcium & concentrates in bone, causing bone cancer & leukemia); half-life= 28.5 y
- Iodine-131 (concentrates in the thyroid gland, causing damaging side effects in large amounts); half-life= 8 d
- Cesium-137 (acts as potassium & concentrates in body fluids, causing damage at high levels); half-life= 30.2 y
Linus Pauling
won Nobel Peace Prize in 1962 for being a major advocate of banning atmospheric atomic bomb tests
when was the nuclear test ban treaty signed?
in 1963, signed by major nations (minus France & People’s Republic of China)
thermonuclear reactions
nuclear fusion reactions that require extremely high temperatures and pressures
uses of nuclear energy
- electricity
- propel sea vessels (mainly military)
- medical diagnostics/procedures
consequences of nuclear energy
- build-up of nuclear waste
- potential use of spent nuclear fuel for weapons
- possibility of nuclear plants malfunctioning
where is the largest environmental cleanup effort in the US?
Hanford, WA
what are the 3 nuclear plant malfunctions that have occurred?
- Three Mile Island (Harrisburg, PA)
- partial meltdown causing little radioactive fallout
- Three Mile Island (Harrisburg, PA)
- Chernobyl
- fire & release of radioactivity causing serious radioactive fallout
- Chernobyl
- Fukushima
- 2011 earthquake caused tsunami waves that flooded the plant & town, causing a partial meltdown, cooling system failure, & serious radioactive fallout
- Fukushima
