Warm – Up:

Warm – Up:Warm – Up:Think about the terms “radiation” and “radioactivity.” On a piece of paper,

please write down at least 3 things you think of when you hear these terms.

(Hint: what you write down does not have to be a definition: it can be things that use radiation, what

these terms make you think of, etc.)

After today you will be able to… Describe the 3 different types of radiation

α - alpha β - beta - gamma

Explain the significance of an isotope’s radioactive half life

4.4 Unstable Nuclei and Radioactive Decay

Vocabulary

Radioactivity-the spontaneous emission of radiation from a substance

Radiation-rays and/or particles emitted from radioactive material

Nuclear reactions- changes in an atom’s nucleus

4.4 Unstable Nuclei and Radioactive Decay

Types of Radiation

Alpha radiation - stream of high energy alpha particles

alpha particles consist of 2 protons and 2 neutrons and are identical to helium-4 nucleus.

symbol: 4He 2+

2

not much penetrating power, travel a few centimeters, stopped by paper, no health hazard

4.4 Unstable Nuclei and Radioactive Decay

mass number decreases by 4 atomic number by 2

alpha decay: 226 Ra 222Ra + 4 He 88 86 2

Example: Uranium-238

4.4 Unstable Nuclei and Radioactive Decay

Beta radiation high speed electrons

To form beta radiation a neutron splits into a proton and an electron

The proton stays in nucleus and the electron propels out at high speed.

Symbol 0e- 0β

-1 -1

100 times more penetrating then alpha radiation, pass through clothing to damage skin

4.4 Unstable Nuclei and Radioactive Decay

Beta decay: 131I 131 Xe + 0β 53 54 -1

Example: Astatine-220

4.4 Unstable Nuclei and Radioactive Decay

Gamma radiation similar to X rays doesn’t consist of particles

symbol: 0 0

penetrates deeply into solid material, body tissue, stopped by Pb or concrete, dangerous

usually emitted with alpha and beta radiation no mass or electrical charge emission of gamma rays by themselves cannot

result in the formation of a new atom

Radioactive or Not: That is the

question!

What determines if something is radioactive or not?

Radioactive or Not: That is the

question!

What determines if something is radioactive or not?

Atoms with an unstable proton to neutron ratio will undergo radioactive decay according to

their half life!

4.3 How atoms differ Isotopes:

Isotope – atoms of the same element with different numbers of neutrons (different mass #)

Examples: Carbon – 12 Carbon – 14 (used in carbon dating)

Hydrogen – 1 (protium) Hydrogen – 2 (deuterium) Hydrogen - 3 (tritium)

Before You Go: Please answer the following questions on a

piece of paper and hand it to me before you leave!!!

1. What is one thing you learned today about radioactivity or one misconception that is now cleared up?

2. What is one question you still have about radioactivity or radiation?