Download - Basic Anatomic & Nuclear Physics
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INTRODUCTION TO MEDICAL PHYSICS
(BMB 34103)
Lecturer : SITI AFIFAH MOHSHIM(STAM)
Lecture 1.1 : STRUCTURE OF ATOM AND NUCLEUS ATOMIC MASS AND ENERGY UNITS
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TOPIC 1
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TOPIC 1.1
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1.1 STRUCTURE OF ATOM AND NUCLEUS
Atoms are composed of three types of particles : protons, neutrons, and electron.
The electron is constantly spinning around the center of the atom (called the nucleus).
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1.1 ATOMIC MASS AND ENERGY UNITS
The atomic mass (ma) is the mass of an atom, most often expressed in unified atomic mass units (amu).
amu is a unit of mass used to express atomic and molecular masses.
atomic mass atomic weight
unified atomic mass unit (amu) = dalton (Da) = universal mass unit
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1.1.1 Early Models Of Atom
Who had been discover the atom?1) Isaac Newton
a) The atom was a tiny, hard, indestructible sphere
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1.1.1 Early Models Of Atom
Who had been discover the atom?2) JJ Thomson
a) Suggested a model of the atom as a volume of positive charge with electrons embedded throughout the volume (the seeds in a watermelon) See figure.
b) Plum Pudding Model
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1.1.1 Early Models Of Atom Who had been discover the atom?
3) Rutherforda) Performed a critical experiment (Geiger
Marsdens) showing that Thomson's model couldn't be correct.
Rutherford atomic model
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1.1.1 Early Models Of Atom
Who had been discover the atom?
4) Neils Bohr When the atom was
excited the electron could jump to a higher level.
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1.1.1 Early Models Of Atom
Spectra When the electron came back down, it released energy in the form of light
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1.1.2 Atomic Number
Number of the nucleons (neutrons and protons) in the
nucleusMass NumberA
Number of the neutron in the nucleusNeutron NumberN
Number of the proton in the nucleus (or the number of
electrons outside the nucleus).
Atomic NumberZ
ExplanationMeaningSymbol
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1.1.2 Atomic Number
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1.1.2 Atomic Number
93
No of Electrons(equal to Z
modified by charge number)
808104No of Neutrons(equal to A-Z)
56893No of Protons (equal to Z)
Elemental Symbol
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1.1.2 Atomic Number
Example 1.1 : Consider the isotope F19.
(a) What is the name of this element? (b) How many protons are in this isotope? (c) How many neutrons are in this isotope?
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1.1.3 Composition of Structure Nucleus
It contains two kinds of fundamental particles: protons (+ve charge) and neutrons (no charge)
Atom
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1.1.3 Composition of Structure
0.5115.486 x 10-49.109 x 10-31Electron
939.571.0086651.6750 x 10-27Neutron
938.281.0072761.6726 x 10-27Proton
MeV/c2amukg
MASSES
PARTICLE
Charge & Mass; Atomic Masses
Conversion Factors :
1 amu = 1.660559 x 10-27kg 1 amu = 931.5 MeV/c21 Newton = 1 kg m/sec21 Joule = 1 Newton-meter 1 MeV = 1.6022 x 10-13 joules
The rest energy of a particle is given by
E = mc2E = rest energym = mass c = speed of light ~ 2.99792x108 m/s
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1.1.4 Electron Binding Energies And Energy Levels
Binding Energy Binding energy is defined as the amount of
energy that must be supplied to a nucleus to completely separate its nuclear particles (nucleons).
The loss in mass, or mass defect, is due to the conversion of mass to binding energy when the nucleus is formed.
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1.1.4 Electron Binding Energies And Energy Levels
Binding Energy
Mass Defect = [ Z (mp + me) + (A Z) mn ] - matom
Binding energy can be calculated using :
Binding Energy (BE) = (Mass Defect)
amuMeV
15.931
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1.1.4 Electron Binding Energies And Energy Levels
Example 1.2 :
Calculate the mass defect for lithium-7. Given the mass of lithium-7 is 7.016003 amu.
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1.1.4 Electron Binding Energies And Energy Levels
Electron Binding Energy Electron binding energy, or ionization
potential, is the energy required to remove an electron from an atom, molecule, or ion, and also the energy released when an electron joins an atom, molecule, or ion.
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1.1.4 Electron Binding Energies And Energy Levels
Energy Levels of Atoms The electrons near the nucleus are the lowest
energy level and would have the greatest binding energy.
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1.1 STRUCTURE OF ATOM AND NUCLEUS ATOMIC MASS AND ENERGY
UNITS
Exercise : Calculate the following in
relation to Uranium-235. One Uranium-235 atom has a mass of 235.043924 amu.
a. Mass defect b. Binding energy
( )U23592