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