History of radioactivity and its decay...

4. In 1896
Got Noble prize in 1903.
He discovered Natural
Radioactive element (Uranium)
In 1898
Got Noble Prize in 1903
She discovered Artificial radioactive elements.
Polarium and Radium.

6. Radioactivity was first Discovered by Hennery
Becqueral in 1896.
Exdently Becqueral left some uranium salts on a
photographic plate (x-ray film)wrapped in a black
paper and was lied in a Dark room.
When he developed the Photographic plate, he
found that the plate was affected.
Later he repeated the experiment with other salts
of uranium and its salts emits invisible radiations
which can pass through paper glass etc ,and affect
the radiographic plate.

7. Marie and Pierre Curie spent years purifying
radioactive elements.
They discovered new radioactive elements
Radium and Polonium in1898.
To be continued……

8. • Unstable nucleus:
• Has excess energy.
• Wants to go to “ground state.”
• Becomes stable by emitting
ionizing radiation.

9. What is Radioactivity
Radioactivity is the process by which a Nucleus
of an Unstable atom loses Energy by emitting
ionizing Radiation.
 Radiation is released in form of Particles or
Electromagnetic waves.
A material that spontaneously emits this kind of
radiation- Which includes the emission of Alpha
particles, Beta particles and Gamma rays is
considered Radioactivity.

10. Ex-Uranium EX-Radio Cobalt

11. It is the property of natural occuring
radionuclides
ex- Uranium (i.e the spontanous emission of
radiation from an unstable nuclie is known as
Natural radioactivity.
Its half life is too long.
This is the process of emission of radiations from
artifically occuring isotops when they are
bombarded with sub-atomic particles or high
levels of x rays or gamma rays.
Ex-Radio cobalt.

12. RADIOACTIVE
DECAY

13. Radioactive decay is a process by which a
radioactive atoms emits particles and energy
to reach a more stable configuration.
Atoms may emits Alpha and Beta particles
from the nucleus or may spontaneous splits
into different isotopes producing Gama or
Neutron radiation.
Unaffected by temperature, pressure,
physical state, etc

14. Nuclides with
same atomic
number but
different mass
number is called
Isotopes

15. The elements which under go
radioactive decay process are
called Radio-isotopes

16. Alpha Particles (2n, 2p)
Beta Particles (e- or +)
(x or gamma rays)
Paper Lead
Types of radioactive decay-
Aluminium
object

17. When an unstable nucleus emits an alpha
particle it undergoes alpha decay.
The resulting new nucleus is an isotope.
An alpha particles is identical to that of helium
nucleus.
It contains 2 protons and 2 neutrons.
 

 HeXX N
A
ZN
A
Z
4
22
4
2
(unstable) (more stable) (Alpha decay)

18. Example: Uranium-238 undergoes alpha decay than
Uranium-238 decays to make a new isotope -
thorium and an alpha particle.

19. Two types of beta decay are known:
1) β – (minus) Decay
 Neutron in the nucleus is converted into a proton
 Atomic number increases by 1 (new element)
 During this conversion an electron and an
antineutrino are ejected from the nucleus
 Also known as electron emission
 An example of β- decay is:
Th234
90
Pa
234
91
e0
-1  v
__
Electron Antineutrino

20. 2) β + Decay (positron emission)
 Proton in the nucleus is converted into a
neutron
 Atomic number decreases by 1 (new element)
 During this conversion a positron and a
neutrino are ejected from the nucleus
 Also known as positron emission
 An example of β+ decay is:
Positron Neutrino
Na
22
11
Ne
22
10
e0
1  v

21. When an atom decay by emitting alpha or
beta particles to form a new atoms the nucleus
of new atom formed may still have too much
energy to be completely stable.
The atom will emits Gamma rays to release
that energy.
Gamma rays are not charged particles like
alpha and beta particles.
There are no change in atomic number and
mass number.