This presentation is about nuclear chemistry.

2. The radioelements must exist in various forms different
from each other by their masses and by their nuclear
properties . About 40 atoms with different half-lives were
discovered , for which 12 places in periodic table of
elements.
 The atoms of an element which have same atomic
number but different mass number or atomic masses.

3. Isotopes that emits radiation are called radioactive or radioisotopes.
A nucleus is stable if it cannot be transformed into another configuration
without adding energy from the outside . thousands of nuclides that exist,
about 250 are stable. A plot of the number of neutrons versus the number
of protons for stable nuclei reveals that the stable isotopes fall into a narrow
band . This band called STABILITY BAND.

4.  The lighter stable nuclei, in general, have equal numbers of protons and
neutrons. For example, nitrogen-14 has seven protons and seven neutrons.
Heavier stable nuclei, however, have increasingly more neutrons than
protons . For example:iron-56 has30 neutrons and 26 protons, an n:p ratio
of 1.15, whereas the stable nuclide lead-207 has 125 neutrons and 82
protons, an n:p ratio equal to 1.52. This is because larger nuclei have more
proton-proton repulsions, and require larger numbers of neutrons to provide
compensating strong forces to overcome these electrostatic repulsions and
hold the nucleus together.

7. Isotopes
Atomic number
Mass number Electrons
Protons
Neutrons
35Cl 17 35 17 17 35 - 17 = 18
36Cl 17 37 17 17 37 - 17 = 20

8. EXAMPLE OF NEON ISOTOPES.
Neon has three isotopes with atomic number 10 and mass numbers, 20, 21 and
22.
Isotopes Atomic number Mass number
Electrons
Protons Neutrons
20Ne 10 20 10 10 20 - 10 = 10
21Ne 10 21 10 10
21 - 10 = 11
22Ne 10 22 10 10
22 - 10 = 12

9.  The word isobar means equally heavy is taken from the Greek isos=equal, and
barys=heavy .
 The atoms which have same mass number but different atomic number are called
isobars.
 Hence, as isobars have different atomic number, therefore, they have a different
number of electrons, and their chemical properties are different.

11. MASS EXCESS OF SOME ELEMENTS IN amu and MeV,,,,,,
Nuclide
Mass
excess
(amu)
Mass
excess
(MeV)
In49 -0.0896 -83.5
Sn50 -0.0943 -87.8
Sb51 -0.0958 -89.2
Te52 -0.0967 -90.1
I53 -0.0944 -87.9
Xe54 -0.0915 -85.2
Cs55 -0.0870 -81.0

12. Atoms which have same number
of neutrons.
 Due to different mass number
and atomic number, they show
different chemical and
physical properties.

13. “The breaking of a large nucleus into smaller pieces is called fission”
• Many heavier elements with smaller binding energies per nucleon can
decompose into more stable elements that have intermediate mass numbers
and larger binding energies per nucleon—that is, mass numbers and binding
energies per nucleon that are closer to the “peak” of the binding energy
graph near 56 . Sometimes neutrons are also produced

15. • Chain reactions of fissionable materials can be controlled and sustained
without an explosion in a nuclear reactor
• Any nuclear reactor that produces power via the fission of uranium or
plutonium by bombardment with neutrons must have at least five
components: nuclear fuel consisting of fissionable material, a nuclear
moderator, reactor coolant, control rods, and a shield and containment
system

16. • Nuclear fuel consists of a fissionable isotope, such as uranium-235, which
must be present in sufficient quantity to provide a self-sustaining chain
reaction
• Nuclear reactors require a fuel with a higher concentration of U-235 than is
found in nature; it is normally enriched to have about 5% of uranium mass
as U-235. At this concentration, it is not possible to achieve the supercritical
mass necessary for a nuclear explosion

17. • A nuclear moderator is a substance that slows the neutrons to a speed that is
low enough to cause fission.
• Modern reactors in the US exclusively use heavy water ( 1 2 H2 O) or light
water (ordinary H2O), whereas some reactors in other countries use other
materials, such as carbon dioxide, beryllium, or graphite.

18. • A nuclear reactor coolant is used to carry the heat produced by the fission
reaction to an external boiler and turbine, where it is transformed into
electricity.
• Two overlapping coolant loops are often used; this counteracts the transfer
of radioactivity from the reactor to the primary coolant loop

19. • Nuclear reactors use control rods to control the fission rate of the nuclear
fuel by adjusting the number of slow neutrons present to keep the rate of
the chain reaction at a safe level.
• Control rods are made of boron, cadmium, hafnium, or other elements that
are able to absorb neutrons. Boron-10

20. • Reactors are equipped with a containment system (or shield) that consists of
three parts:
1. The reactor vessel, a steel shell that is 3–20-centimeters thick and, with the
moderator, absorbs much of the radiation produced by the reactor
2. A main shield of 1–3 meters of high-density concrete
3. A personnel shield of lighter materials that protects operators from γ rays
and X-rays