Types of Radiation and Unstable Nuclei
I. Chemical and Nuclear Reactions• Chemical reactions only involve an atom’s electrons
• Nuclear reactions involve changing an atom’s nucleus
• Nuclear reactions release a million times more energy than chemical reactions
• Unlike chemical reaction, nuclear reactions are not affected by temperature, pressure, or a catalyst.
II. Nuclear Vocabulary
• Radioactivity – the process of emitting radiation. • Radiation - rays and particles emitted by a
radioactive source.• Radioisotopes – isotopes of atoms with unstable
nuclei and emit radiation to obtain a more stable nuclei
• Radioactive decay - Unstable nuclei losing energy by emitting radiation in a spontaneous process.
• Nucleon – refers to both protons and neutrons
III. Which Isotopes are Radioactive?
• Small Nuclei - Atoms which contain up to 20 protons (up to Calcium) are usually stable.
• Large Nuclei - Larger nuclei tend to be radioactive. All nuclei with 84 or more protons (Polonium and up) are radioactive. For example, all isotopes of Uranium are radioactive.
• Atoms with more neutrons than protons - There are radioactive nuclei that have less than 84 protons. These nuclei have more neutrons than protons. For example, Carbon-12 (6 protons and 6 neutrons) is stable, while Carbon-14 (6 protons and 8 neutrons) is radioactive.
IV. Why Does an Atom Undergo Radioactive Decay?
• Radioactive atoms emit radiation because their nuclei are unstable.
• The stability of the nucleus depends on the neutron to proton ratio
• Neutrons vs. protons graph stable nuclei found in a region called the band of stability.
V. Types of Radiation – Alpha Radiation
• Alpha radiation are attracted to the negatively charged plate
• Alpha particles contain two protons and two neutrons (A helium nucleus)
• Blocked by paper• Least penetrating form of radiation (only travels a
few centimeter in the air)• Carry +2 charge• Symbolized by He or 4
242
VI. Types of Radiation – Beta Radiation
• Beta radiation attracted to the positively charged plate
• Carry –1 charge• Beta particles are fast moving electrons• Blocked by metal foil or wood• Medium penetration power (travels a few
meters in the air)• Symbolized by e or 0
-1 0-1
VII. Types of Radiation – Gamma rays
• Gamma rays are high energy radiation that possess no mass.
• Possess no electrical charge and are not deflected by magnetic or electrical fields.
• Not completely blocked by lead or concrete• The most penetrating and damaging type of
radiation• Carry no charge• Symbolized by
0 0
IX. Electrostatic Force• Electrostatic force is when like charges repel and opposite
charges attract.
X. Strong Nuclear Force
• The strong nuclear force or nuclear force is an attractive force that acts between all nuclear particles that are extremely close together.
• It keeps the nucleus together.
Remember Mass Number and Atomic Number
C14 6
Mass number
Atomic number
XI. Writing and Balancing Nuclear Equations
• In a balanced nuclear equation, mass numbers and atomic numbers are conserved.
Example• Th Ra + He
– Notice the mass numbers and atomic numbers add up to the same on both sides of the equation
230 90
226 88
42
VIII. Electron Capture
• Electron capture occurs when a nucleus of an atom draws in an electron.
• Rb + e → Kr
• Also known as Beta capture
0- 1
8137
8136
Practice
1. Zr e + ?
2. Po He + ?
3. ? Rn + He
4. Ca e + ?
5. Cm He + ?
9741Nb
Pb214 82
Ra226 88
Sc4721
Pu240 94
0-1
218 84
4 2
222 86
97 40
4 2
0-1
47 20
4 2
244 96