1. Radioactivity The Nucleus Isotopes Radioactivity
Three kinds of emission
Nuclear Processes

2. Rutherford’s Experiment

3. Results of the Experiment
Most of the particles were undeviated
Some particles were deviated at angles less than 90⁰
Only a few particles were deviated at angles more than 90⁰

4. Meaning of Results Atom is mostly empty space
Most of its mass is concentrated at the nucleus
The nucleus is very small

5. The Atom The nucleus Protons Neutrons
The number of protons = number of electrons = atomic number, Z
While the number of protons + neutrons = atomic mass, A

6. Isotopes Have the same atomic number but different atomic mass
A.k.a. nuclide

7. Radionuclide Some isotopes Are unstable Too many nucleons
Too much energy
Have spontaneous nuclear decay
Emit energetic particles or rays
The phenomenon of their decay is known as radioactivity

8. Nature of Radioactivity

9. Nature of Radioactivity
Random
There is a constant probability of decay of the nucleus of an atom
Spontaneous
Decay is not affected by environmental factors like temperature and pressure.

10. Graph of Radioactive Decay
Count rate is decreasing with time
Random
Fluctuations in the graph
Graph is not a smooth curve