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PHYSICAL BACKGROUND ATOMIC STRUCTURE, NUCLEONS AND ACTIVITY

DR. MOHAMMED MOSTAFA EMAM

INAYA MEDICAL COLLEGE (IMC)RAD 243- LECTURE 1

LECTURES & CLASS ACTIVITIES

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16-02-2015 DR. MOHAMMED MOSTAFA EMAM 2

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TOPIC

ISOTOPES

RADIOISOTOPES

RADIOACTVE DECAY

HALF LIFE


INTRODUCTION

• INTRODUCTION ABOUT RADIATION:

Radiation is energy in the form of waves orstreams of particles.

Based on the interaction with the matterthere are two types of radiation

1. Ionizing radiation

2. Non- ionizing radiation16-02-2015 DR. MOHAMMED MOSTAFA EMAM 4

TYPES OF RADIATION


ATOMS

• Where all matter begins?

Atoms are the basic building blocks ofthe all the matters in this world.

All things both living and non livingbegins with atoms only.

Atoms are elements like oxygen ,hydrogen and carbon.


STRUCTURE OF AN ATOM

Proton


ISOTOPES

• An isotopes is a variant of a particularchemical element.

• Isotopes of an element consists of a samenumber of protons and different number ofneutrons.

• For example, hydrogen has 3 isotopes:

Hydrogen 1 : 1 proton and no neutrons

Hydrogen 2 : 1 proton and 1 neutron

Hydrogen 3 : 1 proton and 2 neutrons16-02-2015 DR. MOHAMMED MOSTAFA EMAM 8

Isotope is stable when it has a same number of neutrons and protons.

The number of protonspresent in atom is calledas Atomic Number.The number of protonsand neutrons present inatom is called asNuclear Number.


RADIOISOTOPEDEFINITION: • Radioactive isotope or radioisotope, natural

or artificially created isotope of a chemicalelement having an unstable nucleus that decaysemitting α, β and ϒ rays until stability reached.

• A radioisotope is an isotope of an elementthat undergoes spontaneous decay and emitsradiation as it decays.

• During the decay process , it becomes lessradioactive overtime, eventually becomingstable.

• Once an atom reaches a stable configuration,it no longer gives off radiation.


RADIOACTIVE DECAY

• Radioactive decay is the process in which anunstable atomic nucleus loses energy byemitting radiation in the form of particles orelectromagnetic waves.

• There are two forms of radioactive decay

Natural radioactivity

Artificial radioactivity


RADIOACTIVE DECAY• Natural radioactivity:

This is the spontaneous disintegration ofnaturally occurring radio–nuclides to form amore stable nuclide with the emission ofradiations of alpha, beta and gamma.

• Artificial radioactivity:

This is the spontaneous disintegration of anuclide when bombarded with a fast movingthermal neutron to produce a new nuclide withthe emission of radiations of alpha, beta andgamma and a large amount heat.


RADIOACTIVE DECAY

• There are three types of radioactive emission:

α decay

β decay

ϒ decay


RADIOACTIVE DECAY


RADIOACTIVE DECAY

Proton mass ≈ Neutron mass

= 1 Atomic Mass Unit


RADIOACTIVE DECAYα – decay:

• Alpha particles consists of large mass.Alpha decay occurs when the atom ejects aparticle from the nucleus, which consists oftwo neutrons and two protons.

• When alpha decay occurs, the atomic numberdecreases up to 2 and the mass decreases by4 and electrical charge of +2.


RADIOACTIVE DECAY

• Another example:


RADIOACTIVE DECAYβ – decay:

β particles are consists of small mass and -1 electrical charge. It is mainly emitted bynucleus.

In basic β – decay, a neutron is turned intoa proton and an electron is emitted from thenucleus.

The atomic number increases by 1 andmass decreases slightly.


RADIOACTIVE DECAY

ϒ – emission:

Gamma radiation have high energy,short wave length. It accompanies with alphaand beta emission, but it’s usually not shownin a balanced nuclear reaction.

Gamma is an electromagnetic wave orphoton which has no electrical charge andhas great penetrating power.

Gamma decay takes place when there isresidual energy in the nucleus following α orβ decay.


RADIOACTIVE DECAY

• The residual energy is released as a photon ofgamma radiation. Gamma decay generallydoes not affect the mass or atomic number ofa radioisotope.

• Gamma radiation is similar to that of X- rays.

• E.g., Cobalt- 60(Co-60). Gamma rays arefocused on the tumor to destroy it.


HALF LIFE

• Radioactive half-life is the time it takes half the radioactive atoms present to decay.

Before After one half-life16-02-2015 DR. MOHAMMED MOSTAFA EMAM 21

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