Bellringer Compare and explain in complete sentences what is nucleus.

HW SUBMIT YOUR HW FROM TUESDAY

NUCLEAR CHEMISTRY

Introduction to Nuclear Chemistry  Nuclear chemistry is the study of the structure of and the they undergo.

Chemical vs. Nuclear Reactions Chemical ReactionsNuclear Reactions Occur when bonds are broken Occur when nuclei emit particles and/or rays

Chemical vs. Nuclear Reactions Chemical ReactionsNuclear Reactions Occur when bonds are brokenOccur when nuclei emit particles and/or rays Atoms remain unchanged, although they may be rearranged Atoms often converted into atoms of another element

Chemical vs. Nuclear Reactions Chemical ReactionsNuclear Reactions Occur when bonds are brokenOccur when nuclei emit particles and/or rays Atoms remain unchanged, although they may be rearranged Atoms often converted into atoms of another element Involve only valence electrons May involve protons, neutrons, and electrons

Chemical vs. Nuclear Reactions Chemical ReactionsNuclear Reactions Occur when bonds are brokenOccur when nuclei emit particles and/or rays Atoms remain unchanged, although they may be rearranged Atoms often converted into atoms of another element Involve only valence electronsMay involve protons, neutrons, and electrons Associated with small energy changes Associated with large energy changes

Chemical vs. Nuclear Reactions Chemical ReactionsNuclear Reactions Occur when bonds are brokenOccur when nuclei emit particles and/or rays Atoms remain unchanged, although they may be rearranged Atoms often converted into atoms of another element Involve only valence electronsMay involve protons, neutrons, and electrons Associated with small energy changesAssociated with large energy changes Reaction rate influenced by temperature, particle size, concentration, etc. Reaction rate is not influenced by temperature, particle size, concentration, etc.

The Discovery of Radioactivity (1895 – 1898):  found that invisible rays were emitted when electrons bombarded the surface of certain materials.  Becquerel accidently discovered that phosphorescent salts produced spontaneous emissions that darkened photographic plates

The Discovery of Radioactivity (1895 – 1898):   isolated the components ( atoms) emitting the rays  – process by which particles give off  – the penetrating rays and particles by a radioactive source

The Discovery of Radioactivity (1895 – 1898):  identified 2 new elements, and on the basis of their radioactivity  These findings Dalton’s theory of indivisible atoms.

The Discovery of Radioactivity (1895 – 1898):  – atoms of the element with different numbers of  – isotopes of atoms with nuclei (too / neutrons)  – when unstable nuclei energy by emitting to attain more atomic configurations ( process)

Alpha radiation  Composition – Alpha particles, same as helium nuclei  Symbol – Helium nuclei, He, α  Charge – 2+  Mass (amu) – 4  Approximate energy – 5 MeV  Penetrating power – low (0.05 mm body tissue)  Shielding – paper, clothing 4 2

Beta radiation  Composition – Beta particles, same as an electron  Symbol – e -, β  Charge – 1-  Mass (amu) – 1/1837 (practically 0)  Approximate energy – 0.05 – 1 MeV  Penetrating power – moderate (4 mm body tissue)  Shielding – metal foil

Gamma radiation  Composition – High-energy electromagnetic radiation  Symbol – γ  Charge – 0  Mass (amu) – 0  Approximate energy – 1 MeV  Penetrating power – high (penetrates body easily)  Shielding – lead, concrete

Review of Atomic Structure NucleusElectrons 99.9% of the mass 1/10,000 the size of the atom 0.01% of the mass

Review of Atomic Structure NucleusElectrons 99.9% of the mass 1/10,000 the size of the atom 0.01% of the mass Composed of protons (p + ) and neutrons (n 0 ) Composed of electrons (e - )

Review of Atomic Structure NucleusElectrons 99.9% of the mass 1/10,000 the size of the atom 0.01% of the mass Composed of protons (p + ) and neutrons (n 0 ) Composed of electrons (e - ) Positively chargedNegatively charged

Review of Atomic Structure NucleusElectrons 99.9% of the mass 1/10,000 the size of the atom 0.01% of the mass Composed of protons (p + ) and neutrons (n 0 ) Composed of electrons (e - ) Positively chargedNegatively charged Strong nuclear force (holds the nucleus together) Weak electrostatic force (because they are charged negatively

Chemical Symbols  A chemical symbol looks like…  To find the number of, subtract the from the C 6 14

Nuclear Stability  Isotope is completely stable if the nucleus will spontaneously.  Elements with atomic #s to are.  ratio of protons:neutrons ( )  Example: Carbon – 12 has protons and neutrons

Nuclear Stability  Elements with atomic #s to are.  ratio of protons:neutrons (p + : n 0 )  Example: Mercury – 200 has protons and neutrons

Nuclear Stability  Elements with atomic #s are and.  Examples: and

Alpha Decay  Alpha decay – emission of an alpha particle ( ), denoted by the symbol, because an α has 2 protons and 2 neutrons, just like the He nucleus. Charge is because of the 2.  Alpha decay causes the number to decrease by and the number to decrease by.  determines the element. All nuclear equations are. 4 2

Alpha Decay  Example 1: Write the nuclear equation for the radioactive decay of polonium – 210 by alpha emission. Step 1: Write the element that you are starting with. Mass # Atomic # Step 2: Draw the arrow.Step 3: Write the alpha particle.Step 4: Determine the other product (ensuring everything is balanced).

Alpha Decay  Example 2: Write the nuclear equation for the radioactive decay of radium – 226 by alpha emission. Step 1: Write the element that you are starting with. Mass # Atomic # Step 2: Draw the arrow.Step 3: Write the alpha particle.Step 4: Determine the other product (ensuring everything is balanced).

Beta decay  Beta decay – emission of a beta particle ( ), a fast moving, denoted by the symbol or. β has insignificant mass ( ) and the charge is because it’s an.  Beta decay causes change in number and causes the number to increase by. 0 -1

Beta Decay  Example 1: Write the nuclear equation for the radioactive decay of carbon – 14 by beta emission. Step 1: Write the element that you are starting with. Mass # Atomic # Step 2: Draw the arrow.Step 3: Write the beta particle.Step 4: Determine the other product (ensuring everything is balanced).

Beta Decay  Example 2: Write the nuclear equation for the radioactive decay of zirconium – 97 by beta decay. Step 1: Write the element that you are starting with. Mass # Atomic # Step 2: Draw the arrow.Step 3: Write the beta particle.Step 4: Determine the other product (ensuring everything is balanced).

Gamma decay  Gamma rays – high-energy radiation, denoted by the symbol.  γ has no mass ( ) and no charge ( ). Thus, it causes change in or numbers. Gamma rays almost accompany alpha and beta radiation. However, since there is effect on mass number or atomic number, they are usually from nuclear equations.

Transmutation  – the of one atom of one element to an atom of a different element ( decay is one way that this occurs!)

Review Type of Radioactive Decay Particle Emitted Change in Mass # Change in Atomic # Alpha α He -4-2 Beta β e 0+1 Gamma γ

Half-Life  is the required for of a radioisotope’s nuclei to decay into its products.  For any radioisotope, # of ½ lives% Remaining 0100% 150% 225% 312.5% 46.25% % %

Half-Life

 For example, suppose you have 10.0 grams of strontium – 90, which has a half life of 29 years. How much will be remaining after x number of years?  You can use a table: # of ½ livesTime (Years)Amount Remaining (g)

Half-Life  Or an equation!

Half-Life  Example 1: If gallium – 68 has a half-life of 68.3 minutes, how much of a mg sample is left after 1 half life? ________ 2 half lives? __________ 3 half lives? __________

Half-Life  Example 2: Cobalt – 60, with a half-life of 5 years, is used in cancer radiation treatments. If a hospital purchases a supply of 30.0 g, how much would be left after 15 years? ______________

Half-Life  Example 3: 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 mg sample will remain after days? ______________

Half-Life  Example 4: The half-life of polonium-218 is 3.0 minutes. If you start with 20.0 g, how long will it take before only 1.25 g remains? ______________

Half-Life  Example 5: A sample initially contains mg of radon-222. After 11.4 days, the sample contains mg of radon-222. Calculate the half-life.

Nuclear Reactions  Characteristics:  Isotopes of one element are into isotopes of another element  Contents of the change  amounts of are released

Types of Nuclear Reactions  decay – alpha and beta particles and gamma ray emission  Nuclear - emission of a or

Nuclear Fission  - of a nucleus  - Very heavy nucleus is split into approximately fragments  - reaction releases several neutrons which more nuclei  - If controlled, energy is released (like in ) Reaction control depends on reducing the of the neutrons (increases the reaction rate) and extra neutrons ( creases the reaction rate).

Nuclear Fission  - 1 st controlled nuclear reaction in December st uncontrolled nuclear explosion occurred July  - Examples – atomic bomb, current nuclear power plants

Nuclear Fusion  - of a nuclei  - Two nuclei combine to form a heavier nucleus  - Does not occur under standard conditions ( repels )  - Advantages compared to fission -,  - Disadvantages - requires amount of energy to, difficult to  - Examples – energy output of stars, hydrogen bomb, future nuclear power plants

Uses of Radiation  Radioactive _______________ - Carbon - ____ used to determine the ________ of an object that was once alive.  ___________________________ of diseases – Iodine – 131 used to detect _________________ problems, technetium – 99 used to detect ___________ tumors and ____________ disorders, phosphorus – 32 used to detect __________ cancer.  Treatment of some _______________________ (cobalt – 60 and cesium – 137) – cancer cells are more ________________________ to radiation than normal, healthy cells

Uses of Radiation  X-rays  Radioactive ________________ (used in research to _______ chemicals)  Everyday items – thorium – 232 used in ______________________, plutonium – 238 used in _______________________, and americium – 241 in ___________________________________

ACTIVITY START READING FROM PAGE 256 WRITE VOCABULARY, WRITE NEW WORDS, CONCEPTS, THEIR MEANING Work on questions from the study guide