Nuclear Chemistry

Hadrons (Optional)
Hadron is a composite particle made up of quarks and mesons held together by strong force.

Subatomic Particles (Optional)
1) Positron (anti-electron) : The positron has charge + 1 and same mass as electron (negligible).

Notations : β+ e+.When electrons and positrons collide, they give rise to 2 or more gamma photon rays.

2) Lepton : Particles that are subject to Pauli's Exclusion Principle . consists of (e- ve)(undefinedμ- vμ)(undefinedt vt)

3) Neutrinos : It is electrically neutral, with half integer spin .  Neutrinos are leptons along with charged electrons , muons(μ) , taus ; and come in three flavors : electron neutrinos(ve)(-1/2 spin) , muon neutrinos(vμ) (+1/2 spin), tau netutrinos (vt) (+1/2).

For every electron neutrino produced, a positron is produced and for every electron anti-neutrino produced , an electron is produced as well.

4) Anti-Neutrino : Anti-Neutrino helps in conservation of Lepton Number.

5) Quark : Quarks combine to form hadronic particles, of which protons and neutrons are the most stable . types or flavors : up , down , strange , charm , top , bottom.

6) Anti-Quark : Some properties of anti-quark have equal magnitude and opposite sign of that of quarks.

7) Mesons : A Meson is composed of a quark and anti-quark, bound together by strong interactions .Mesons are very unstable . The longest life of a meson could be a hundredth of a microsecond . Charged mesons decay to give electrons and Neutrinos . Uncharged Mesons may decay to give photons.

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Nuclear Coulombic Barrier
The force of repulsion between the nucleus and approaching α particle is called as Nuclear Coulombic Barrier.

Repulsive Potential Energy = V = (Z1e)(Z2e) / d = (Z1Z2)e2/ d

The Nucleus
Nuclear Size

r = r0A1/3{where r = nuclear size, A = Atomic mass number}

r0= 1.4 x 10-15 m= 1.4 fm

Nucleus Proton Ratio

Nuclei with even number of protons and neutrons are abundantly found.

Nuclei with even - odd combination are intermediately found.

Nuclei with odd - odd combination are rare.

Nuclear Stability

The Nucleus Proton Ratio gives us an idea of the stability of a nucleus.

As atomic Number increases, the N/P ratio increases. (This is because the more number of neutrons are added than protons .)

All nuclei above atomic number 82, are beyond stability belt and are radioactive.

Radioactive Decay
Radioactive Decay takes place in order to stabilize the nucleus. In the process the atom may gain or loss it's entities.

α Emission

It is equivalent to a Helium Atom. An α emission eliminates 4 amu and 2 Z from an atom.

Almost all elements above atomic number 82 decay by α emission. It leads to the formation of isodiapher i.e. difference in number of Neutrons and Protons remains same.

β Emission

It is equivalent to conversion of a neutron to proton. Thus, A β emission adds 1 Z to an Atom. A neutron is converted into a proton by removal of negative charge from it.

Elements having a very high N/P ratio and that lie above the stability belt, undergo β emission , as neutrons are converted into protons are added.

Positron Emission

It is equivalent to a particle having no mass but positive charge. This particle is called as a positron.

It is actually the conversion of proton to neutron by removing it's positive charge.

A positron emission or β+ emission eliminates 1 Z from the atom.

Electron Capture (K Capture)

It is equivalent to an electron from K shell. In this emission, an electron from K shell is captured by the nucleus. AS an effect, a proton is converted into a positron. Electron capture mostly occurs with Heavier elements.

γ Emission

It is equivalent to a neutron. γ Emission causes no change.

Nuclear DisIntegration
Rate of DIsintegration

Rate of DIsintegration = - dN/dt

Rate α N

Rate = λ N

Integrated Rate Law

λ = [2.303/t] log10 [N0/N]

N0/N gives the ratio of number of atoms, or the ratio of number of moles.

Simultaneous Decay

Decay pf an equimolar binary mixture.

2.303 log10[N1/N2] = (λ2 - λ1) t

Half Life Period

t1/2undefined= 0.693 / λ  Also ; at any point ; N = 2-n N0

Average Life Period

λ' = 1/λ = t1/2 / 0.693 = 1.44 t1/2

Radioactivity
Unit

The standard unit of radioactivity is Curie. The biological effect of radiation is measured in rads.

Parallel Radioactive Disintegration

Suppose a Nuclei A splits into nuclei X and Y, then

λA = λX + λY

Fractional Yield of X = λX / λA

Fractional Yield of Y = λY / λA

Successive Radioactive Disintegration

Daughter Nuclei, formed by parent nuclei also undergoes disintegration.

Suppose A forms B and B forms C with λ1 and λ2 as disintegration constants ;

N1/N2 = (λ2- undefinedλ1) / λ1

Secular Equilibrium

N1 / N2 = λ2 / λ1

i.e. radioactivity is not affected through the half-lives

Disequilibrium

Fission and Fusion Reactions
Nuclear Fusion 

Nuclear fusion is the process in which lighter nucleus combines to form a heavier nucleus, which results in the emission of enormous amount of energy.

e.g. A Hydrogen bomb releases 17.6 MeV energy.