Unit 5 The Structure of Matter

1. Unit 5 The Structure of Matter Chapter 16 The Atom

2. 16C – The Nuclear Atom • Objectives: • Define radioactivity and identify important kinds of nuclear radiation • Describe the various processes of nuclear decay and how each affects the atom • Use nuclear decay equations to illustrate each kind of decay process • Discuss one application of nuclear decay t hat helps save lives • Compare and contrast nuclear fission and fusion, including the conditions under which each occurs • Discuss the difficulties of developing electrical generation using fusion energy • Assignments: Outline, Worksheet and Section Review page 405

3. Nuclear Radiation • Antoine Henri Becquerel • French physicist who discovered nuclear radiation and radioactivity • Won Nobel Prize in Physics • Too many or too few neutrons in an atom leads to less stability • Nuclear Chemistry • The study of changes that occur in the atomic nuclei • Began by the accidental discovery of radioactivity • The emission of nuclear radiation • Rays and particle emitted by unstable nuclei • Experiments led to the discovery of alpha particles, beta particles, and gamma rays • symbolized by the Greek letters

4. Nuclear Decay • Larger nucleus = excess energy • Gamma Decay • No change in the atom except for reducing the amount of energy in its nucleus • Can be very damaging to organic molecules found in living things • Molecules that absorb gamma rays can be destroyed as the energy disrupts bond between atoms

5. Alpha Decay • More significant then gamma • Loses an alpha particle, equal to helium • Atom’s nucleus loses two protons and two neutrons, reducing its atomic number by 2 and its mass number by 4 • Because its atomic number has changed, the atom is now an isotope of a DIFFERENT element • Once the alpha particle hits something it gains electrons and becomes a normal helium atom; however it tends to interact with other atoms very easily, damaging chemical bonds as it rips electrons away from other atoms and molecules

6. Beta Decay • Ratio of protons and neutrons is too large to be stable • A neutron changes to a proton • Emits a beta particle, a high energy electron • The mass number stays the same • The atomic number increases by one changing the atom into an isotope of another element

7. Decay Equations

8. What Can Stop Radiation?

9. Nuclear Bombardment Reactions • Happens when a nucleus is struck by a high energy particle or another nucleus • Different than nuclear decay because bombardment reactions release millions of times more energy and many more particles than alpha or beta decay • Almost always artificially induced in special nuclear reactions and particle accelerators

10. Nuclear Fission • Occurs when a large, unstable nucleus splits into smaller, more stable nuclei, releasing energy • Forced to occur artificially in a nuclear reactor • Can also occur spontaneously, although rare • As neutrons are released they are absorbed by other nuclei which also fission releasing more free neutrons causing a chain reaction • In a controlled nuclear chain reaction an immense amount of energy can be release to do useful work • Fission bombs are better known as atomic bombs or nuclear bombs

11. Nuclear Fusion • The opposite of fission • Smashing smaller nuclei together to form a large one • Produces even more energy than fission • Fusion bombs, better known as hydrogen bombs or thermonuclear bombs