1. Radioactivity
Chapter 19

2. Forces inside an atom 1) Electromagnetic force:
a) attracts electrons(-) to protons(+)
b) protons repel each other (+,+)
c) long range
2) Strong force:
attraction of nucleons for each other
(protons & neutrons = nucleons)
strongest force in the universe but..
very short range

3. Nuclear Force interactions
1) All nucleons attract each other
2) Only protons
repel each other
3) More neutrons = more attraction with out adding any
repulsion
(Neutrons called nuclear cement)

4. Nuclear Force interactions
4) more neutrons add stability to atoms unless……
too many neutrons w/o protons nearby
neutrons that are by themselves decay
the neutron spits out an electron and turns into a proton
the electron that shoots out is a beta particle (beta radiation)

5. Nuclear Force interactions
H-3 (tritium) decays to Helium

6. Nuclear Force interactions
Neutron mass is greater than proton mass by slightly more than 1 electron (1/1800 amu)
Extra mass is converted to energy Ve

7. Law of conservation of Matter??!!
The extra matter is not destroyed……
it is converted into energy
E = mc2
E is the energy produced
m is the amount of mass converted
C is the speed of light

8. Beta radiation 1) produced by beta decay
2) = a very fast moving electron
3) can penetrate human skin
4) damages DNA = mutations & cancer
a) most dangerous to growing cells
b) babies & children
c) cancer cells ….so beta radiation used to treat cancer

9. Alpha radiation -origin
1) Happens when too few neutrons
2) Nucleus unstable bcs strong force
can’t reach across large nuclei
but Electromagnetic force can!

10. Alpha radiation- origin
3) pieces of large unstable nucleus
break off
4) the pieces are alpha particles
5) alpha particles consist of
2 protons & 2 neutrons

11. Alpha radiation-effects
Atom changes to different element
Atomic number decreases by 2
Atomic mass decreases by 4 amu

12. Alpha radiation -characteristics
1) largest radiation particle & + charge
so can’t penetrate through skin
2) can damage internal tissues if inhaled or swallowed
3) can cause cancer… radon gas
4) alpha particles pick up electrons to
become helium w/i a few cm

13. Gamma radiation Pure energy ….has no mass
Very high energy light wave (not visible)
Generated by the sun
Can penetrate most materials
Can harm & kill cells
Can cause cancer, birth defects & shortened life span