Isotopes are variants of elements with the same number of protons but different numbers of neutrons, resulting in different atomic weights. They can be stable or unstable, with unstable isotopes undergoing radioactive decay to achieve stability, emitting radiation in the process. Radioactive isotopes have significant clinical applications, such as in diagnostics and therapy, but also pose hazards including immediate health effects and long-term risks like carcinogenesis.

1. Dangerous

2. Definition
 Atoms with same atomic
number/number of proton but
different atomic weight (number
of protons+neutrons).
 So atoms may be different atomic
weight due to different neutron
number.

3.  Isotopes are variants of a
particular chemical element which
differ in neutron number. All
isotopes of a given element have
the same number of protons but
different numbers of neutrons in
each atom.

4.  The term isotope is formed from
the Greek roots isos ("equal") and
topos ("place"), meaning "the
same place“. So the meaning
behind the name is that different
isotopes of a single element
occupy the same position on
the periodic table.

5. Examples of isotope

7.  The number of protons within
the atom's nucleus is
called atomic number and is equal
to the number of electrons in the
neutral (non-ionized) atom. Each
atomic number identifies a
specific element, but not the
isotope; an atom of a given
element may have a wide range in
its number of neutrons.

8.  The number of (both protons and
neutrons) in the nucleus is the
atom's mass number, and each
isotope of a given element has a
different mass number.

9. Types of isotope
 Stable isotope/ non radioactive
 Unstable isotope/ radioactive
isotope

10. Stable isotope
 The first evidence for multiple
isotopes of a stable (non-
radioactive) element was found
by J. J. Thomsonin 1913 as part of
his exploration into the
composition of canal rays
(positive ions)

11.  Stability of an isotope depends on
the definite neutron to proton ratio
which is specific for a specific
atom.
 In low atomic weight atoms
stability achieved with neutron to
proton ratio around one

12.  In case high molecular weight
stability usually achieved by more
neutron than proton and the ratio
more than one (>1).
 Naturally occurring isotopes are
predominantly stable isotope.

13. Examples of stable isotopes

14. Unstable isotope (raidoactive)
 The existence of isotopes was
first suggested in 1913 by
the radiochemist Frederick Soddy
based on studies of
radioactive decay chains that
indicated about 40 different
species referred to
as radioelements (i.e. radioactive
elements) between uranium and
lead

15. Unstable isotope (raidoactive)
 Have the capacity to emit
radiation
 These isotopes neutron and
proton ratio far from stability ratio
 Isotopes of heavy elements are
usually unstable example: radium,
urenium
 Aim of radioactivity is to become
stable

16. Example

18. Radioactive decay
 It is the spontaneous
decomposition or disintegration of
an unstable isotope of a definite
element in an attempt to become
a stable isotope with
simultaneous emission of
radiation (α,β,γ) and formation of
new element.

19. Radioactivity
 It is the spontaneous emission of
accelerated particles (radiation)
from an unstable isotope by radio
active decay.

20. Mechanisms of radio active decay
 Alpha decay: heavy atoms (atomic
number >70) may emit alpha
particles from radio active
nucleus.
 beta decay: atomic number <60
may emit beta particles.
 Positive beta decay: in case of
artificial isotope positive beta
particles (positron) emit.

21. Half life of radioactive isotope
Radioactive isotope Half life
14Carbon 5760 yrs
3Hydrogen 12 yrs
60Cobalt 5.3yrs
51Chromium 28days
32Phosphrus 14days
131Iodine 8days
99Technetium 8hrs
It is the time required for a radioactive
isotope to reduce its radioactivity half of
its initial value

22. Clinical use/importance of radio-
active isotope
 Diagnostic use- to diagnosis
diseases
 Therapeutic use- radiotherapy
treatment for malignancy
 Use in tracer technique- to study of
metabolic pathway
 Measurement of volume & spaces-
ECF volume, blood volume
 Measurement of regional blood flow
 Sterilization of medical instrument

23. Diagnostic use
 Iodine uptake test for thyroid
disorder
 Radio immune assay for hormonal
disorder
 Organ scanning- bone, brain, thyroid
 Absorption test- iron, Vit B12
 RBC half life measurement
 Isotope renogram for measurement
of GFR, renal clearance

24. Radiation hazards/disadvantage of
radio isotope
 Immediate hazard:
1. Bone marrow depression and
immune suppression
2. Damage to intestinal mucosa
causing diarrhoea & malabsorption
3. Baldness, rough scaly skin
4. In pregnancy: fetal growth
retardation, congenital
malformation fetal or neonatal
death

25.  Delayed hazards: carcinogenesis,
sterility, neonatal death
 Genetic effect: DNA damage,
mutation

26. Radiosensitive tissue
 These are most rapidly dividing
tissue. Such as
Bone marrow
Gonads
Lymph node
Skin
Intestine