IGN SUDARYADI, M.Kes.Rad-Biologi UGM

Chemical versus Nuclear Reactions:

1. 2Na+ + H2O ----> 2NaOH + 2H+

3-5 eV in this reaction

2. 42He + 94Be ----> 126C + 10n10 million eV in this reaction

In a nuclear reaction, we have to balance both mass and proton number.Transmutation : changing one element into anotherTransmutation : changing one element into another

3517Cl + 10n ------> 3215P + 42He

3216S + 10n ------> 3215P + 11p

Chemical reactions involve changes in the outer electronic structure of the atom

whereas nuclear reactions involve changes in the nucleus

Discuss the history of Radioactivity

A series of incidents spark the birth of nuclear radiology Einstein: Relativity theory (1905), quantum theory Einstein: Relativity theory (1905), quantum theory Discovery of x-rays in 1895 by W.C. Roentgen Discovery of radioactivity by Henri Becquerel in 1896 Discovery of radium by Pierre and Marie curie in 1898 Rutherford: (1902) transmutations "changing one element

to another

Isotopes are atoms of the same element that differ in mass. They have the same number of protons and electrons but have a

different mass which is due to the number of neutrons. 1. All radio isotopes have a particular kind of radiation emission

2. Energy and mass are equivalent (Einstein) higher mass, higher energy3. All radio nuclides have a characteristic energy of radiation4. All radio nuclides possess a characteristic rate of decay

Dealing with reactions in the outer ring that compromise and produce chemical reactions.__________________________________________

atomic mass units chargeatomic mass units charge(amu)

__________________________________________proton 1.007594 +electron 0.000549 -neutron 1.008986 none__________________________________________

14C6 (8)

6 Protons- Atomic Number (determines what the element is)

(8) ~ 8 Neutrons

14 = P+N = Atomic Mass

Isotope (of a given element) same atomic number, different atomic masses (different # of neutrons)

146C 126C 23592U 23892U

Stable Isotope Non-Radioactive Isotope (not decomposing)

Radioisotope or Radionuclide unstable isotope that spontaneously decays emitting radiation

Radioactive decay: not affected by temperature or environmental conditions

mZE 11H 42He

E- elementm massz - atomic number (# of protons in the nucleus)

All hydrogen atoms have one proton__________________________________________1

1H 21H 31H__________________________________________

stable stable radioactivedeuterium tritium

mass = 1 mass=2 mass=3no neutron 1 neutron 2 neutronsno neutron 1 neutron 2 neutrons1 proton 1 proton 1 proton1 electron 1 electron 1 electron__________________________________________12

6C 136C 146C__________________________________________stable stable radioactivemass=12 mass=13 mass=146 neutrons 7 neutrons 8 neutrons6 protons 6 protons 6 protons6 electrons 6 electrons 6 electrons__________________________________________

Half-Life

Half-life is the amount of time needed for the activity to reach

f e t ln ( )2T1/2

0.60

0.80

1.00

activity to reach one half of the original amount.

f1

2

tT1/2

0 20 40 60 80 100

0.00

0.20

0.40

One half-life

Two half-lives

0.007

Days

Radiation is everywhereCosmic

Inhaled Radon

We live in a sea of radiationRocksRadioactive Elements

PlantsBodies

1. When is an Isotope Stable, or Why are Some Isotopes Radioactive?

Radioactive isotope Stable Isotope

RULES

A. All nuclei > 84 protons are unstable (the nucleus gets too big, too many protons)

B. Very Stable: Atomic Number 2, 8, 20, 50, 82 or 126

C. Isotopes with Proton=Neutrons are more stable

# of neutrons

# of protons

unstable

unstable

Belt of stability80

0

Where do Radionuclides/Stable Isotopes Come From?

Fission: Splitting the Nucleus to Release Energy and Sub Atomic Particles

Decay Series: Series of Reactions That Ends With a Stable Isotope

U, Th, Pa, U, Th, Ra, Rn, Po, Pb, Bi, Po, Pb, Bi, Po, Pb

Fission Reaction Used for Radio DatingFission Reaction Used for Radio Dating

238U Geologic Time (106 years)

t 1/2 = 4.5x109 yr

14C Up to 20,000 B.P. (before present)

t 1/2 =5700 yr

147N + 10n 146C + 11H (14C being produced all the time in the upper atmosphere)

146C 147N + 0-1e (beta particle)

Living Tissue 14C/12C, Tissue ratio same as atmospheric ratio

Dead Tissue 14C/12C< 14C/12C

tissue atmospheretissue atmosphere

Clock starts when you die

home