basic anatomic & nuclear physics

1Intro To Medical Physics_STAM [Lec01 (1.1)]

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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

Intro To Medical Physics_STAM [Lec01 (1.1)]

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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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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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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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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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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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Example 1.2 :

Calculate the mass defect for lithium-7. Given the mass of lithium-7 is 7.016003 amu.

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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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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

basic anatomic & nuclear physics

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