Nuclear Reactions & Difference of Nuclear and Chemical Reactions

1. Nuclear Reactions & Difference of Nuclear and Chemical Reactions by: Kerem ERYILMAZ Adnan ÖZTÜREL

2. Nuclear Reactions Chemical reactions all involve the exchange or sharing of electrons, they never have an influence on the nucleus of the atom.  Nuclear reactions involve a change in the nucleus.  There are forces in the nucleus that oppose each other, the "Strong" force holding Protons and Neutrons to each other and the electrostatic force of protons repelling other protons.  Under certain arrangements of protons and neutrons the electrostatic force can cause instability in the nucleus causing it to decay. It will continue to decay until it reaches a stable combination.

3. This graph shows the stable nuclei in red.  There are several things to notice: - There are no stable nuclei with an atomic number higher than 83 or a  neutron number higher than 126. - The more protons in the nuclei, the more neutrons are needed for stability.  Notice how the stability band pulls away from the P=N line. - Stability is favored by even numbers of protons and even numbers of neutrons. 168 of the stable nuclei are even-even while only 4 of the stable nuclei are odd-odd.

4. Unstable nuclei, called radioactive isotopes, will undergo nuclear decay as it becomes more stable.  There are only certain types of nuclear decay which means that most isotopes can't jump directly from being unstable to being stable.  It often takes several decays to eventually become a stable nuclei.   • Types of Radioactive Decay • When unstable nuclei decay, the reactions generally involve the emission of a particle and or energy.  Below is a table describing the types of nuclear decay. Notice that for each type of decay, the equation is balanced with regard to atomic number and atomic mass. In other words, the total atomic number before and after the reaction are equal.  And the total atomic mass before and after the reaction are also equal.

5. Particle Name alpha particles What is it? helium nuclei   or Relative penetrating power 1 stopped by the skin but very damaging due to ionization

6. Happens to nuclei with  Z>83 The 2 p+ 2n loss brings the atom down and to the left toward the belt of stable nuclei.

7. Particle Name beta particles What is it? high speed electron              or            Relative penetrating power 100 penetrates human tissue to ~1cm 

8. Happens to nuclei with high neutron:proton ratio A neutron becomes a proton causing a shift down and to the right on the stability graph  

9. Particle Name gamma rays What is it? high energy photon Relative penetrating power 10000highly penetrating but not very ionizing Generally accompanies other radioactive radiation because it is the energy lost from settling within the nucleus after a change. Since gamma rays do not affect the atomic number or mass number, it is generally not shown in the nuclear equation.

10. Particle Name positron emission What is it? positron Relative penetrating power 100

11. Happens to nuclei with a low neutron:proton ratio A proton becomes a neutron causing a shift up and to the left

12. Particle Name electron capture What is it? inner shell electron Relative penetrating power  no release of energy or particle Happens to nuclei with a low neutron: proton ratio A proton becomes a neutron causing a shift up and to the left.  Always results in gamma radiation

13. This graph shows all the trends of decay and the band of stable nuclei.  There are some exceptions to the trends but generally a nuclei will decay following the trends (in multiple steps) until it becomes stable.  For example 92U238 will go through 8 alpha emissions and 6 beta emissions (not all in order) before becoming 82Pb206

14. The steps a nuclei follows in becoming stable is called a radioactive series.  The series for 92U238 is shown below as an example.

15. Differences Between Nuclear and Chemical Reactions Six Differences between nuclear reactions and chemical reactions. Nuclear Reactions Chemical Reactions • Protons and neutrons react 1. Electrons react outside nucleus. • inside nucleus. 2. Elements transmute into other 2. The same number of each kind of elements. atom appear in the reactants and products. 3. Isotopes react differently. 3. Isotopes react the same. 4. Independent of chemical 4. Depend on chemical combination. combination. 5. Energy changes equal 10^8 kJ. 5. Energy changes equal 10 - 10^3 kJ/mol. 6. Mass changes are detectable. 6. Mass reactants = mass products.