Nuclear Chemistry Chapter 21
Objectives Define radioactivity. Explain trends in the relative stability of nuclei. Complete half-life calculations. Write, balance, and interpret nuclear reactions. Identify types of radioactive decay. Explain how fusion and fission occur. Discuss applications of nuclear chemistry in everyday life. Outline the potential hazards of nuclear energy.
Chemical Reactions vs Nuclear Reactions
Nuclear Reactions The mass must be conserved The atomic number must be conserved.
Nuclear Stability Certain numbers of neutrons and protons are extra stable n or p = 2, 8, 20, 50, 82 and 126 Like extra stable numbers of electrons in noble gases (e- = 2, 10, 18, 36, 54 and 86) Nuclei with even numbers of both protons and neutrons are more stable than those with odd numbers of neutrons and protons All isotopes of the elements with atomic numbers higher than 83 are radioactive All isotopes of Tc and Pm are radioactive
Types of Nuclear Decay
Energy of Radioactivity
Nuclear Stability and Radioactive Decay Beta decay 14C 14N + 0b 6 7 -1 Decrease # of neutrons by 1 40K 40Ca + 0b 19 20 -1 Increase # of protons by 1 1n 1p + 0b 1 -1 Positron decay 11C 11B + 0b 6 5 +1 Increase # of neutrons by 1 38K 38Ar + 0b 19 18 +1 Decrease # of protons by 1 1p 1n + 0b 1 +1
Nuclear Stability and Radioactive Decay Electron capture decay 37Ar + 0e 37Cl 18 17 -1 Increase number of neutrons by 1 55Fe + 0e 55Mn 26 25 -1 Decrease number of protons by 1 1p + 0e 1n 1 -1 Alpha decay Decrease number of neutrons by 2 212Po 4He + 208Pb 84 2 82 Decrease number of protons by 2 Spontaneous fission 252Cf 2125In + 21n 98 49
Complete the following nuclear reaction equations.
Complete the following nuclear reaction equations. Alpha decay for Thorium-232 Plutonium-244 undergoes beta decay Radon-222 decays into Astatine-210 Francium-223 emits a gamma particle Complete the following nuclear reaction equations.
What Are Your Questions?
What is Half-Life? The amount of time it takes for half a given amount of material to radioactively decay into something else.
Initial Amount After 1 Half-Life After 2 Half-Lives After 3 Half-Lives
Based solely on the following half-lives, which radioactive atom listed is the most radioactive? C-14 (5730 yrs) Ra-226 (1620 yrs) U-238 (4.5 million yrs) Po-214 (1.6 ms) P-32 (14 days)
Radioactive Dating Radiocarbon Dating 14N + 1n 14C + 1H 7 1 6 14C 14N + 0b + n 6 7 -1 t½ = 5730 years Uranium-238 Dating 238U 206Pb + 8 4a + 6 0b 92 -1 82 2 t½ = 4.51 x 109 years = t½ l 0.693
A 4. 5 gram sample of radon decomposes over 3 half lives A 4.5 gram sample of radon decomposes over 3 half lives. How much of the sample remains?
The half-life of C-14 is 5730 years The half-life of C-14 is 5730 years. How long will it take for 50% of 25g of C-14 to decompose? How long will it take for 75% to decompose?
An artifact contains 12. 5% of the original amount of C-14 An artifact contains 12.5% of the original amount of C-14. How old is this sample? (C-14 half-life is 5730 years.)
The half-life of the beta particle emitter tritium, 3H, is 12 years The half-life of the beta particle emitter tritium, 3H, is 12 years. How much of a 1.00 g sample of 3H remains after 48 years?
What Are Your Questions?
Fusion and Fission https://www.youtube.com/watch?v=FU6y1XIADdg
Nuclear Fusion Reactor https://www.youtube.com/watch?v=MGj_aJz7cTs
Medical Uses for Radioactive Isotopes
Nuclear Weapons Use nuclear reactions to create an intense explosion. The Manhattan Project Project the ran from 1942-46 to develop atomic bombs.
Nuclear Disasters Three Mile Island (1979) Chernobyl (1986) Partial Meltdown in Pennsylvania Chernobyl (1986) Reactor 4 meltdown in Ukraine Time 3:06 Fukushima (2011) Three of six nuclear reactors melted down in Japan as a result of a tsunami
What Are Your Questions?