Nuclear Chemistry—chemistry of the nucleus Chemistry of the Nucleus Marie Curie

How does a nuclear reactor work?

How does a small mass contained in this bomb cause…… Nuclear Bomb of 1945 known as “fat man”

…this huge nuclear explosion?

Is there radon in your basement?

I. Radiation/Radioactivity A.What is it? 1.The release of energy and/or matter from the nuclei of atoms. 2.If something is radioactive it is giving of energy or particles 3.Radioactive decay = the spontaneous break down of an atom’s nucleus; may cause the atom to to turn into a different kind of atom.

B. Review of atom 1. nucleus contains protons & neutrons & electrons spin around nucleus 2. proton mass = ____ neutron = ____ electron = ___ 3. proton charge =____ neutron = _____ electron = ___ 4. atomic # = ________ 5. atomic mass = ______ + _______ 6. Isotopes: atoms with the same # of protons, but different number of neutrons than mass number.

Notation

H H H

Isotopes of Carbon

C. Why are atoms radioactive? 1. The nucleus is unstable due to imbalance of protons and neutrons or a large # of neutrons and protons. 2. The strong force (holds the neutrons and protons together) & weak force (holds protons together) are not strong enough. 3. elements with atomic # > 83 = radioactive

II. Main Types of Radioactive Decay Alpha  Beta  Gamma 

A. Alpha Decay * Emission of alpha particle --  : Nucleus releases a particle that is 2 protons & 2 neutrons = Helium nucleus. (4 amu, 2+ charge) Proton # deceases by 2 & mass decreases by 4 Notation: can travel a few inches through air can be stopped by a sheet of paper, clothing.

Alpha Decay

Alpha Decay

B. Beta Decay Emission of Beta particles  electrons ejected from the nucleus when neutrons decay into a proton. Proton # increases by 1, mass stays same. Notation: Can be stopped by aluminum foil or a block of wood.

Beta Decay

C. Gamma Decay Emission of Gamma radiation--  Gamma rays are electromagnetic waves or energy They have no mass. Gamma radiation has no charge. Most Penetrating, can be stopped by 1m thick concrete or a several cm thick sheet of lead.

Examples of Radioactive Decay Alpha Decay Po  Beta Decay C  Gamma Decay Ni 

Band of Stability Number of Neutrons, (N) Number of Protons (Z)

III. Radioactive Half-Life : A.What is it: 1.The time it takes for half of a radioactive sample of atoms to change into something else. 2. represented by t 1/2

3. After one half -life there is 1/2 of original sample left. 4. After two half-lives, there will be 1/2 of the 1/2 = 1/4 the original sample.

Half-life of some isotopes Isotope Half-Life Radiation Emitted Carbon-14 5,730 years  Radon days  Uranium x 108 years  Uranium x 109 years 

Example You have 100 g of radioactive C-14. The half-life of C-14 is 5730 years. How many grams are left after one half-life? How many grams are left after two half-lives?

Problem A sample of 3x10 7 Radon atoms are trapped in a basement that is sealed. The half-life of Radon is 4 days. How many radon atoms are left after 32 days?

B. Half-life Graphs 1.Can use graph to figure out half-life of an atom 2.As the parent isotope decreases the daughter isotope increases

C. Uses of Radioactive dating 1.Dating Fossils 2.Dating rocks 3.Finding a safe isotope to put in someone’s body 4.Determining when it is safe to go somewhere that there has been Radiation.

IV. Fission A.Splitting of an atomic nucleus into 2 smaller nuclei with the release of a large amount of energy and radiation. 1.Then energy is from the forces that held the nucleus together and also lost mass.

2.E= mc2– Einstein’s equation Energy = mass x the speed of light 2 There is the loss of some mass that is converted into energy 3.Nuclear chain reaction: continuous series of fission rxns. * as one nucleus splits, neutronsAre released to split more nuclei

B.Uses of fission 1. Nuclear power plants– use fission of Uranium-235 to create heat that create steams that turns a turbine that is used to create electricity. 2. Nuclear weapons: use fission to create immense amounts of energy (an explosion) to destroy people Critical mass: amount of U-235 that will sustain a chain reaction.

VI. Uses/Exposure to Radiation A.Uses 1. Fission– nuclear energy 2. Alpha/beta/gamma particles/rays: a.Sterilize food (kill microorganisms) b. detect leaks in pipes c.Medical uses (imaging, detecting disease, tracing Blood circulation, treating cancer

B. Exposure A.Background radiation All around us from stars, rocks, etc. Earth’s atmosphere and magnetic field stops most of the cosmic radiation.

B.Other sources X-rays, other medical procedures, nuclear accidents

V. Fusion A.The joining of 2 small atomic nuclei to form a single nucleus releasing a large amount of energy and radiation. 1.Need temps of millions of degrees Celsius 2. Occurs naturally on/in stars 3. Attempting to use it here for energy—but many problems

4. Occurs mostly with Hydrogen Atoms (lightest atoms) (drawing)

VI. Stars A.Energy Source 1.Fusion: Hs fuse to make He 2.Produces huge amounts of light and heat B. Properties 1.Color & 2. Temperature—blue (hot!!) red (cool), yellow (medium), White (cool) 3. Brightness—affected by size and surface temperature ---if something is closer, it appears brighter ---Real brightness can be calculated 4. Size/Mass—cannot be measured directly, brightness is used

C. Hertzsprung-Russell Diagrams 1.Graph that helps classify stars 2.Used to estimate size, brightness, temp, distance, and changes in stars.

D. Life Cycle of Stars 1.Star Formation a.Nebula b.Protostar c.Star

E. Star Death 1.Stars change when the H runs out 2.Now He starts to fuse 3.More mass = increased gravity