Types of Radiation and Unstable Nuclei. I. Chemical and Nuclear Reactions Chemical reactions only...

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