St. 9- Nuclear Chemistry 1st, let’s review the parts of the Atom:   Particle Location Charge Proton Electron Neutron

St. 9 Nuclear Chemistry Level 3 Will be able to predict products for alpha and beta decay. Will understand half-life concepts and be able to solve half-life problems Level 2 Recognizes or recalls specific terminology such as: nuclear decay, alpha decay, beta decay, gamma radiation, half-life, fission, fusion Will be able to explain the benefits and risks of radioactivity.

Nuclear Stability Video- 2 min From Discovery Education

How to build an atomic bomb

How to build an atomic bomb Step 1: Obtain 2 pieces of U-235 that are roughly the size of a large grapefruit.

How to build an atomic bomb Step 1: Obtain 2 pieces of U-235 that are roughly the size of a large grapefruit. Step 2: Put them together.

How to build an atomic bomb Step 1: Obtain 2 pieces of U-235 that are roughly the size of a large grapefruit. Step 2: Put them together. Step 3: Stand back.

Radiation: The rays and particles emitted by a radioactive source. Radioactivity: The process by which materials give off radiation by an unstable atomic nucleus. Basically, the nucleus changes (gain or lose protons or neutrons) Radiation: The rays and particles emitted by a radioactive source. Ionizing radiation has enough energy to remove electrons from atoms.

Radioisotopes: The nuclei of unstable isotopes. Stability of a nucleus depends on: Ratio of neutrons to protons in the nucleus. Overall size of the nucleus. An unstable nucleus releases energy by emitting radiation during the process of radioactive decay.

Natural Background Radiation = 295 mRem (82%) Manmade Radiation = medical + consumer products= 63 mRem (18%)

So how are nuclear reactions different from chemical reactions? * In a chemical reaction, atoms lose or share electrons. * In a nuclear reaction, the nucleus changes. * Radioactive decay is spontaneous/no energy input is required.

Types of Radioactive Decay Stopped by:

Things to remember: 1. If adding or taking away protons, it changes the identify of the element. (Proton # is the atomic #, so if the proton # changes, so does the type of element.) 2. Nuclear reactions and chemical reactions are similar in they both have reactants and products However in nuclear reactions, you consider what’s happening in the nucleus of each atom.

Alpha Decay Streams of alpha particles (which are Helium nuclei- 2 protons and 2 neutrons) Since an atom loses two protons, it changes from one element to another. Particles are large enough/low penetrating power Stopped by: paper, clothing, etc. Example:

Beta Decay Streams of high- energy electrons with a negative charge The decaying nucleus turns into a nucleus with an atomic # that is 1 greater than it originally was, but mass is still the same. Example: smaller and lighter than alpha, so move faster/more penetrating power Stopped by thick sheets of metal, wood, or heavy clothing

Gamma Decay Gamma rays are photons emitted from a radioactive nucleus along with alpha or beta particles. They have neither a charge nor mass and are very penetrating. Very high penetrating power, can cause great harm to living cells. Most can pass completely through the human body. Stopped by blocks of lead or concrete (but still very hard to stop

Types of Radiation: Particle Symbol Charge Mass Penetrating Power Stopped By

Balancing Alpha Decay Equations In a balanced nuclear equation, the sum of the mass numbers and the sum of the atomic numbers for the nuclei of the reactant and the products must be equal. MASS NUMBERS Total = 251 = 251 251Cf 247Cm + 4He 98 96 2 Total = 98 = 98 ATOMIC NUMBERS

Equation for Alpha Decay Write an equation for the alpha decay of 222Rn. STEP 1 Write the incomplete equation 222Rn ?s + 4He 86 2 STEP 2 Determine the mass number 222 – 4 = 218 STEP 3 Determine the atomic number 86 – 2 = 84 STEP 4 Determine the symbol of element 84 = Po STEP 5 Complete the equation 222Rn 218Po + 4He 86 84 2

Balancing Beta Decay Equations A beta particle - is an electron emitted from the nucleus. - forms when a neutron in the nucleus breaks down. 1n 0e + 1H 0 -1 1

Equation for Beta Emitter STEP 1 Write an equation for the decay of 42Potassium (a beta emitter) 42K new nucleus + 0e 19 -1 STEP 2 Mass number : (same) = 42 STEP 3 Atomic number: 19 + 1 = 20 STEP 4 Symbol of element 20 = Ca STEP 5 42K 42Ca + 0e 19 20 -1

Check for Understanding: Write the nuclear equation for the beta decay of 60Co. 60Co 60Ni + 0e 27 28 1 beta particle Write the alpha decay for 209Po 209Po 4He + 205Pb 84 2 82

More Practice: 1. If Pb-210 undergoes alpha decay, what new isotope is formed?   2. If Th- 228 is the product of alpha decay what was the original isotope? 3. Write the balanced decay equation for the alpha decay of Pu-234. 4. If Te-130 undergoes beta decay what new isotope is formed? 5. If N-14 is the product of beta decay what was the original isotope? 6. Write the balanced equation for the beta decay of I-129.

Alexander Litvinvenko Former KGB Agent Poisoned with a dose of Polonium-210 Died 3 weeks later

Alpha Particle: Beta Particle: Gamma Ray: A high energy photon emitted by a radioisotope.

Only 264 of the 1500 different known nuclei are stable (do not decay).   Band of Stability: Ratio of neutrons to protons that determines the stability of a nucleus.

For low atomic numbers (below 20): Stable ratio is 1 Above atomic number 20, stable nuclei have more neutrons than protons. The neutron to proton ratio determines the type of decay that occurs. Too many neutrons = beta decay Too few neutrons = electron capture If the nucleus is too large (atomic number above 83) alpha decay occurs.

Half-Life: The time required for one-half of the nuclei of a radioisotope sample to decay to products.   After each half-life, half of the existing radioactive atoms have decayed into atoms of a new element.

Manganese-56 is a beta emitter with a half-life of 2. 6 hours Manganese-56 is a beta emitter with a half-life of 2.6 hours. What is the mass of a 1.0 g sample of manganese-56 at the end of 10.4 hours? The mass of cobalt-60 in a sample is found to have decreased from 0.800 g to 0.200 g in a period of 10.5 years. From this information, calculate the half-life of cobalt-60.

Transmutation: The conversion of an atom of one element to an atom of another element. Transmutation can occur by: Radioactive decay When particles bombard the nucleus of an atom Transuranium Elements: Elements with atomic numbers above 92. All undergo transmutation.

Fission: The splitting of a nucleus into smaller fragments Fission: The splitting of a nucleus into smaller fragments. Can release enormous amounts of energy. Fissionable Isotopes: Uranium-235 and plutonium-239

Chain Reaction: Neutrons produced react with other fissionable atoms, producing more neutrons which react with more fissionable atoms.

Controlled fission (nuclear reactors) involves: Neutron Moderation: Slows down the neutrons. Neutron Absorption: Decreases the number of slow moving neutrons.

18% of the world’s electricity comes from nuclear energy

The US has 104 reactors that provide 20% of the nations electricity

Chernobyl Ukraine – 1986 - Worst reactor accident in history 40 people died from radiation exposure and residual effects

Fusion: Nuclei combine to produce a nucleus of greater mass Fusion: Nuclei combine to produce a nucleus of greater mass. Release much more energy than fission.

Detecting Radiation Radiation cannot be seen, heard, felt or smelled Radiation can be detected by: Geiger Counters Film Badges Scintillation Counters Radioisotopes can be used: In smoke detectors To diagnose medical problems and treat disease To sterilize and preserve food

Sources of Radiation

Alexander Litvinvenko Former KGB Agent Poisoned with a dose of Polonium-210 Died 3 weeks later