Nuclear Chemistry

Reactions Chemical Nuclear Involve electrons Affected external factors (temp, pressure, catalyst) Involve the nucleus Release WAY more energy Not affected by external factors Release about a million times more energy than chemical rxns. Reactions

Electrostatic force Interaction between charged particles like charges repel opposite charges attract Electrostatic force

How does the nucleus stay together?

Attractive force that acts between all nuclear particles that are extremely close together Keeps the nucleus together Much stronger than electrostatic force! Strong Nuclear Force

The emission (and transmission) of energy through space in the form of waves or rays Radiation

Radioactivity Alpha α Beta β Gamma γ Neutron n Proton p Positron β (electron) Gamma γ Neutron n Proton p Positron β 4 2 -1 1 Radioactivity 1 +1

Contain two protons and two neutrons (A helium nucleus) Symbol: Carry +2 charge Least penetrating form of radiation (only travels a few centimeter in the air) Blocked by paper Radioactivity-Alpha

Radioactivity-Beta Fast moving electrons Symbol: Charge: −1 medium penetration (blocked by metal foil or wood) Radioactivity-Beta

Radioactivity-Gamma High energy: waves or rays that possess no mass Symbol: Charge: none Most penetrating and damaging type of radiation not completely blocked by lead or concrete Radioactivity-Gamma

Any element that spontaneously emits radiation (shows signs of radioactivity) Transmutation—changing of an atom’s nucleus such that an new element is formed Transuranium elements-produced through induced transmutation Radioactive

Why does an element undergo transmutation?

Induced Transmutation Before 1919, the only way to change the nucleus, or cause transmutation, was to wait for nature. In 1919, Rutherford was the first to induce transmutation which proved that nuclear reactions could be produced artificially. Can occur by bombarding an atom with alpha particles, protons, or electrons Induced Transmutation

Unstable (Radioactive) nuclei are found outside the band of stability The stability of the nucleus depends on the neutron to proton ratio If a nucleus is unstable, it will emit radiation (decay) to gain stability

Unstable nuclei (those that can be found outside the band of stability) losing energy by emitting radiation in a spontaneous process Radioactive decay

Isotopes of atoms with unstable nuclei and go through radioactive decay to obtain a more stable nuclei Small nuclei—up to 20 protons usually stable Exception: Carbon—14 Large nuclei—tend to be radioactive, based on the ratio of neutrons to protons; ALL nuclei with 83 protons or more are radioactive Radioisotope

In a balanced nuclear equation, mass numbers and atomic numbers are conserved Alpha decay Electron capture or beta capture Th  Ra + He 230 90 226 88 4 2 Rb + e → Kr - 1 81 37 36 Nuclear Equations

Location in the equation Reactant  Product Word Location in the equation Bombardment Reactant Capture Decay Product Emission (emit) Vocab for Equations

Practice Zr  e + ? 2. Po  He + ? 3. ?  Rn + He 4. Ca  e + ? 5. Cm  He + ? -1 218 84 4 2 222 86 97 40 47 20 244 96 Practice

Honors Only- write the equations and solve Uranium-238 undergoing alpha emission Krypton-81 undergoes beta capture Cobalt-59 undergoes neutron bombardment, giving an alpha decay in addition to the new element Would a)emission, b)capture, c) decay, d)bombardment be in the reactant or the product? Honors students write equations in their notes Honors Practice with words

Day 2 of Nuclear Chemistry

Time required for ½ of a radioisotope’s nuclei to decay into its products Equation: NT = N0 (1/2)n NT =Amount remaining at time T N0 = initial amount n= number of half-lives Half-life

Half-Life Formula Example 1 Scientists start with 50.0 g sample of a radioisotope. How much is left after four half-lives?

Honors Half-Life Formula Ex 1 1. Scientists start with 50.0 g sample of a radioisotope. How much is left after four half-lives? NT = N0 (1/2)n NT =Amount remaining at time T N0 = initial amt n= number of half-lives NT = (50.0 g) (1/2)4 NT = 3.125 g NT ≈ 3.13 g

CP Half-Life Formula Ex 1 Scientists start with 50.0 g sample of a radioisotope. How much is left after four half-lives? Half-Life Skip count 50.0 g 25.0 g 12.5 g 6.25 g 3.125 g ≈3.13 g 4 1 2 3

Half-Life Formula Example 2 Iron-59 is used in medicine to diagnose blood circulation disorders. The half-life of iron-59 is 44.5 days. How much of a 2.000 mg sample will remain after 133.5 days?

Honors Half-Life Formula Ex 2 Iron-59 is used in medicine to diagnose blood circulation disorders. The half-life of iron-59 is 44.5 days. How much of a 2.000 mg sample will remain after 133.5 days? NT = N0 (1/2)n NT =Amount remaining at time T N0 = initial amt n= number of half-lives 133.5 days 44.5 days = 3 half-lives NT = (2.000 g) (1/2)3 NT = 0.2500 mg

CP Half-Life Formula Ex 2 Iron-59 is used in medicine to diagnose blood circulation disorders. The half-life of iron-59 is 44.5 days. How much of a 2.000 mg sample will remain after 133.5 days? 133.5 days 44.5 days = 3 half-lives  First figure out the number of half-lives Half-Life Skip count 2.000 mg 1.000 mg 0.5000 mg 0.2500 mg 1 2 3

Carbon-14 Dating Carbon-14 is evenly spread in Earth’s biosphere Carbon-14 is radioactive and undergoes beta decay; half-life of 5730 years Dates carbon-bearing materials up to 62,000 years Carbon-14 Dating

Honors Honors-Using the graph, about what % of carbon-14 remains after 11, 400 years?