1. 18/10/99
Radioactivity
Radioactivity is the release of energy or particles when an atom disintegrates=
fission (meaning to break apart)
The 3 types of radioactivity can be shown by passing emissions through an electrical field:
Phosphorescent zinc sulfide detection screen + –
Strong magnetic or electrostatic field
Lead block
Radioactive substance   

2. Types of radiation: 1) a, 2) b, 3) 
18/10/99
Types of radiation: 1) a, 2) b, 3) 
(In your book p106, p812,)
*Alpha () particles = 42He
*Beta () particles (electrons) are 0–1 
*Gamma (g) rays are symbolized as 00
The symbols are written as you would with all isotopes: the top # is the mass #, and the bottom # is the proton # or charge
For example: an alpha particle has a
mass=4 amu + charge=+2.
Notice its a Helium atom without e-. It has (2 p+, 2 n0, 0 e–)
“alpha decay” means an a particle is given off.
Other decays: beta decay, gamma decay

3. Ra  He Rn + Br  Kr + Pu  He U +
18/10/99
Determine what type of radioactive process is going on in each of the following. Ra
226 88  He 4 2 Rn
222 86 + a) b) c) Br 84 35   -1 Kr 36 + Pu
242 94  He 4 2 U
238 92 +

4. Why are some atoms unstable and undergo radioactive decay, while others do not?
Nuclear instability.
CH 25: Stability depends on the n0:p+ ratio
For small atoms, stability is a 1:1 ratio
For larger atoms, stability should not exceed 1.5:1
Ex: For the large isotope Lead-206
82 protons and 124 neutrons.
The neutron:proton ratio is:
124:82 = 1.512:1
(The # of n = mass # - p # like usual. Then I divided the # of p into the # of n = 124/82)
Is this isotope of lead unstable and radioactive?

5. With all the postive protons repelling each other, why doesn’t the nucleus fly apart? p+ stay in the densely packed nucleus despite the strong *electrostatic repulsion forces produced by the + charged particles (same charges repel). (Since n0 are neutral, they don’t create the electrostatic force (repelling) when they are near p+ or other n0). HOWEVER, the *strong nuclear force acts on the p+ and n0 when they are extremely close together.