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39 Cards in this Set
- Front
- Back
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What is an isotope?
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an atom with a different number of neutrons than an atom, with the same number of protons
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What do they result in?
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a differing atomic mass (or number) for the element
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What type of isotopes is present in periodic table?
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All samples of elements contain a mixture of naturally occurring isotopes in varying amounts, the periodic table mass number is the average of isotopes in most element groups.
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Rules for Average Atomic Mass (AAM):
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-mass used must reflect a real sample
-use weighted average of the masses of the isotope |
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What is Percent abundance (%A)?
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amount of particular type of isotope in a sample.
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What is isotope mass?
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weight of the individual isotope based on the carbon standard.
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What is the equation for Average Atomic mass?
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(%A*MI)+(%A*MI).... etc./100
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Find AAM:
10B: %A=19.78, MI=10.013u 11B: %A=80.22, MI=11.009u |
=10.811u (# on periodic table)
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How stable are radiosotopes?
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most are unstable and spontaneously fall apart or decay into lighter elements.
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How much energy is released?
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a massive amount, as well as subatomic particles
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How long does it take?
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can take a few seconds (like in most synthetic atoms) or billions of years.
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What do nuclear equations represent?
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they represent radioactive decay
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What is the rule for balancing nuclear equations?
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sum of mass #'s and sum of atomic #'s must be equal!
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What are the three types of chemical reactions?
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Alpha decay (α), Beta (β) decay and gamma radiation (γ) decay.
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What is alpha (α) decay?
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-emission of an alpha (α) particle (4mass/2p's He [helium nucleus]) from atoms nucleus
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What is the significance of the 4/2He [helium nucleus]?
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contains no electrons, carrying a charge of 2+, leaving material with 2-.
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Answer this:
226/88 Ra ----> ??? |
----> 222/86 Rn + 4/2 He
(Notice Ra is now Rn due to change of atomic number to 86) |
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Answer this:
a/b X ----> 248/97 Bk + 4/2 He |
a/b X = 252/99 Es
(248+4/97+2 = 252/99, bottom number is atomic number where periodic table says Es) |
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What is beta (β) decay?
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emission of a beta particle (β)
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What is a β particle?
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β particle is an electron "0/-1 e"
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Example:
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3/1 H -----> 3/2 He + 0/-1 e
(notice H turns into He... also NOTE both sides a/b should add up as does here: 3/1 = 3/2+0/-1) |
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What must be done for beta decay to occur?
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a neutron within the nucleus must be converted into a proton as seen in example (top number [mass number] does not change after conversion because protons and neutrons weigh same)
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This is a closer look at the nucleus conversion:
1/0 neutron --------> |
-------> 1/1H (proton) + 0/-1 e (electron or β particle)
Notice they balance! |
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Answer this:
14/6 C ------> |
------> 14/7N + 0/-1 e
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answer this:
90/38 Sr ----> a/b X + 0/-1 e what is a/b X? |
a/b X = 90/39 Y
this is because 39-1 = reactant 38 (Sr) |
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What is gamma radiation (γ)?
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- high energy electromagnetic radiation that often accompanies alpha or beta particle emissions.
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What is its mass and charge?
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gamma rays have neither mass nor charge and is represented as "0/0 γ"
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why does gamma radiation occur?
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it occurs due to excited state in the nucleus caused by alpha or beta decay - the extra energy must be expelled
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Conclusion of Decays:
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alpha decay: mass #:-4 atomic #:-2
# neutrons:-2 beta decay: mass #:0 atomic #:+1 # neutrons:-1 gamma radiation: mass #:0 atomic #:0 # neutrons:0 |
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Does the chemical environment of the nucleus matter in radioactive decay?
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No, since the processes do not involve the atoms electrons (only nucleus) they can occur anywhere. e.g. hydrogen atom can decay in water molecule, hydrogen gas - anywhere.
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can nuclear decay processes (nuclear reactions) be stopped?
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No, nuclear reactions cannot be stopped.
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How do you answer nuclear reactions?
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Use principles of balancing nuclear equations - both sides should add up to the same.
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When does nuclear fission occur?
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Nuclear fission occurs when a highly unstable isotope splits into smaller particles
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What induces nuclear fission?
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nuclear fission is usually induced by a particle accelerator where the atom absorbs a stream of high energy particles such as neutrons, 1/0 n, causing the atom to split into smaller fragments.
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Answer this:
235/92 U + 1/0n ----> 87/35 Br + a/b X + 3(1/0n) what is a/b X? |
add total atomic masses and atomic numbers on first side, then subtract right side from them to yield the element: 146/57 La
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When does nuclear fusion occur?
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nuclear fusion occurs when a target nucleus absorbs an accelerated particle. e.g. hydrogen bomb is nuclear fusion, as well as SUN energy
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What temperatures are needed for nuclear fusion reactions?
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they require very high temperatures to proceed but also produce LARGE amounts of energy
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Example: hydrogen bomb fusion
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6/3 Li + 1/0 n ----> 3/1 H + 4/2 He
Notice total mass numbers and atomic numbers same on both sides. |
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Answer this:
a/b X + 4/2 He -----> 211/85 At + 2(1/0n) what is a/b X? |
a/b X = 209/83 Bi
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