For FDP assignments

2. NUCLEAR CHEMISTRY
Lakshmy.M

3. Natural Radio activity
Henri Becquerel(1852-1908 Marie (1867-1934) and Pierre (1859-1906)
Curie.

4. Natural Radio activity
Radioactive elements
All heavy elements (atomic number >82 U, Th, Ra and Po etc. ) are
unstable therefore they disintegrate to acquire a more stable state.
Radioactivity is unaffected by temperature, pressure and other conditions, hence it is a nuclear property.
α,β-particles and ϒ -rays are emitted from the nucleus.
The rays emitted by radioactive element are called radioactive rays.
The property of emitting these rays is called radioactivity of the elements.
Electrons revolving around the nucleus are not responsible for radioactivity.
It is the phenomenon in which the nucleus of the atom of an element undergoes spontaneous and
uncontrollable disintegration (or decay) and emit α, β or γ-rays.

5. Modes of decay
• The decaying nucleus is called the parent radionuclide (or parent radioisotope),
and the resulting product is known as daughter nuclide.
• α decay
• β decay-
• ϒ decay
• The rate of decay is determined by decay constant. It is denoted by λ .

6. α decay
Emission of α particle or helium
nucleus by which the daughter
nuclide would have atomic
number 2 and mass number 4 less
than that of the parent nuclide.

7. β decay (β plus decay)
.
Beta plus decay (positron
emission)—atomic number 1
less than the parent nucleus.

8. beta minus decay
Beta minus decay (electron
emission)-
atomic number 1 greater than
the parent nucleus.

9. ϒ decay
ϒ decay --- a radioactive
nucleus first decays by the
emission of an α or β particle.
The daughter nucleus that
results is usually left in an
excited state and it can decay
to a lower energy state by
emitting a gamma ray photon.