Chapter 21 - Nuclear Chemistry Flashcards
-Write balanced nuclear equations -Know the difference between fission & fusion -Predict nuclear stability in terms of neutron-to-proton ratio -Calculate ages of objects or amounts of material from data on nucleon abundances using the half-life of a radioactive material -Convert between nuclear activity units -Calculate mass & energy changes for nuclear reactions -Understand the meaning of radiation dosage terms -Understand the biological effects of different kinds of radiation
Give an example of a “nuclear reaction”.
Hydrogen fusion within the Sun’s core makes He & releases gargantuan amounts of energy in the process.
Ex. Used to generate electricity
-Involves changes in the nucleus of an atom
Define “nuclear chemistry”.
The study of nuclear reactions with an emphasis on their uses in chemistry and effects on biological systems.
Ex. Radioactive elements can be used as therapeutic & diagnostic tools
Ex. Radiation therapy
Ex. Thallium stress test
21.1
What two subatomic particles reside in the nucleus?
Protons & neutrons
Nucleons
21.1
All atoms of a given element have the same # of ___; this # is the element’s ______.
Protons; atomic number
21.1
Atoms of a given element have varying # of ____; so they can have different ____, which are the total # of ____ in the nucleus.
Neutrons; mass numbers, nucleons
21.1
Different isotopes of an element are distinguished by their ___.
Mass numbers
Ex. U-234 (very small % abundance), U-235 (0.7% abundance), U-238 (99.3% abundance)
21.1
A _____ is a nucleus w/ a specified # of protons & neutrons.
Nuclide
21.1
Nuclei that are radioactive are called ______.
Radionuclides
21.1
Atoms containing radionuclides are called ______.
Radioisotopes.
21.1
The nuclear properties of an atom depend on …
The number of protons & neutrons in its nucleus.
21.1
Alpha Radiation
A stream of alpha particles.
21.1
Are radionuclides stable?
No. They’re unstable and spontaneously emit particles & electromagnetic radiation. Emission of radiation is 1 of the way in which an unstable nucleus is transformed into a stable one with less energy.
21.1
Write the nuclear equation for the decomposition of Uranium-238. It releases He-4 alpha particles.
Mass numbers must be balanced in all nuclear equations.
238 U —> 234 Th + 4 He
92 90 2
21.1
Define “radioactive decay”.
When a nucleus spontaneously decomposes (decays).
21.1 - Give It Some Thought (p. 895)
What change in the mass # of a nucleus occurs when the nucleus emits an alpha particle?
It decreases by 4.
21.1
Define “alpha particle”.
A particle that’s identical to He-4 nuclei, consisting of 2 protons & 2 neutrons. Symbol:
4He or 4a
2 2
21.1 - Sample Ex.
What product is formed when Ra-226 undergoes alpha decay?
226 Ra —-> 4He + 222 Rn
88 2 86
21.1
Define “alpha particle”.
A particle that’s identical to He-4 nuclei, consisting of 2 protons & 2 neutrons. Symbol:
4He or 4a
2 2
21.1 - Sample Ex.
What product is formed when Ra-226 undergoes alpha decay?
226 Ra —-> 4He + 222 Rn
88 2 86
21.1
What are the 3 most common kinds of radioactive decay?
Alpha, beta, gamma
21.1
What is the charge, mass, relative penetrating power, and nature of radiation for alpha particles?
+2, 6.64 x 10^-24g, 1, 4 over 2 He nuclei
21.1
What is the charge, mass, relative penetrating power, and nature of radiation for beta particles?
-1, 9.11 x 10^-28g, 100, Electrons
21.1
What is the charge, mass, relative penetrating power, and nature of radiation for gamma particles?
0; 0; 10,000; High-energy photons
21.1
Define “beta radiation”.
Streams of beta particles.
21.1
Define “beta particles”. How are they represented in nuclear equations?
High-speed electrons emitted by an unstable nucleus
0e ; 0B
-1 -1
21.1
Write the nuclear equation for the decay by beta emission of I-131.
131I —–> 131Xe + 0e
53 54 -1
21.1
Beta emission is equivalent to the conversion of ….
1n —-> 1p + 0e
0 1 -1
21.1
The electron comes into being only when…
the nucleus undergoes a nuclear reaction.
21.1
Define “gamma radiation (gamma rays)”. How are they represented in nuclear equations?
High-energy photons (electromagnetic radiation of very short wavelength).
0y or just y
0
21.1
What does gamma radiation represent?
The energy lost when the remaining nucleons reorganize into more stable arrangements, so they usually accompany other radioactive emission, although they’re not shown when writing nuclear equations.
21.1
Define “positron”.
A particle that has the same mass as an electron, but an opposite charge.
Produces 2 gamma rays when it collides with an electron.
0e + 0e —> 2 0y
1 -1 0
21.1
Write the equation for the positron emission by the decay of C-11.
11C —-> 0e + 11B
6 1 5
Define “electron capture’.
The capture by the nucleus of an electron from the electron cloud surrounding the nucleus.
21.1
Write the electron capture decay equation of Rb-81.
87 Rb + 0e —-> 81 Kr
37 -1 36
21.1 - Give It Some Thought (p. 897)
Which of the particles listed (Neutron, Proton, Electron, Alpha particle, Beta particle, Positron) result in no change in nuclear charge when emitted in nuclear decay?
The neutron because it’s the only neutral particle listed.
21.1 - Sample Ex.
Write nuclear equation for…
(a) Hg-201 undergoes electron capture
(b) Th-231 decays to form Protactinium-231
(a) 201 Hg + 0e —-> 201 Au
80 -1 79
(b) 231 Th —> 231 Pa + 0e
90 91 -1
21.1 - Practice Ex.
Write a nuclear equation for the reaction in which O-15 undergoes positron emission.
15O —-> 0e + 15N
8 1 7
21.2
Define “nuclear force”.
A strong force of attraction between nucleons.
21.2
Stable nuclei with low atomic numbers (<21) have _____ numbers of neutrons & protons.
Approximately equal
21.2
For nuclei with higher atomic numbers, the number of neutrons _____ the number of protons.
Exceeds
21.2
Define the “belt of stability”.
The area in which all stable nuclei are found. Ends with element 83 (bismuth) because all nuclei was 84+ protons are radioactive.
21.2
How do nuclei above the belt of stability (high neutron-to-proton ratios) move toward the belt?
They lower their ratio by emitting a beta (0e over -1) particle. This decreases the number of neutrons and increases the number of protons in a nucleus.
21.2
How do nuclei below the belt of stability (low neutron-to-proton ratios) move toward the belt?
They use either positron emission (Atom –> Atom + 0e over 1) or electron capture (Atom + 0e over -1 —> Atom). They increase the number of neutrons and decrease the number of protons.
4.2
How do nuclei with atomic numbers greater than or equal to 84 move toward the belt?
Alpha emission. Decreases the number of neutrons and number of protons by 2.
