Radioactivity The Nucleus Isotopes Radioactivity Three kinds of

Radioactivity The Nucleus Isotopes Radioactivity Three kinds of emission Nuclear Processes

Rutherford’s Experiment

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

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

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

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

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

Nature of Radioactivity

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.

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