Outline:4/18/07 Today: Chapter 22 (cont’d) Nuclear Chemistry - Common decay calcs - Biological interactions è Pick up Quiz 9 – from me è Special seminar Wednesday 7:30pm & Thursday 3pm è Last two seminars: 4pm Avg: 7.2

Let do some CAPA questions: #4 – What’s the binding energy of 27 Al? Mono-isotopic: only one isotope It weighs: g/mol (per. table) n Add up the masses of the protons & neutrons & electrons, and subtract the total mass of the individual constituents from the actual mass of the isotope.

Let do some CAPA questions: #4 – What’s the binding energy of 27 Al? How many protons? n Table 22-1 (p. 944): 13    = g/mol 13 How many neutrons? 14 How many electrons? 13 n Difference: = g/mol = g/mol  8.988e10 kJ/g = -2.17e10 kJ/mol

How does this compare to chemical energies? Explosion of tri-nitro-toluene (TNT) has a  H of 1026 kJ/mol… Explosion of tri-nitro-toluene (TNT) has a  H of 1026 kJ/mol… n The amount of energy used to hold together 1 mole of Al nuclei is: kJ/mol… kJ/mol…

Binding Energy per Nucleon

Let do some CAPA questions: #8 – Which are the stable isotopes? Check proton-to-neutron ratio Check for odd-odd p & n Check for heavies (Z>83) Check for artificial elements (Tc, 3 H)

Worksheet #13 - Question % of 1000g = 0.2 g 14 C 0.2 g  1mol/14g = mol 14 C N/N 0 = 7.65e20 / 8.60e21 =  ln (0.0889) =  k t   2.42 =  × 10  4 yr  1 t = 8.60e21 atoms 14 C mol 14 C  6.022e23 atoms/mol t = 20,000 yr

Worksheet #13 - Question e20 14 C atoms = N0 N0 t = 1/52 yr  N = 7.65e20 e  kt  7.65e20 e  × 10  4 (1/52) N = ? N = e20 N  N 0 = 1.78e15

Why a thin layer? High energy, sub-atomic (small) : highly penetrating High energy: highly ionizing 

What effect does it have on biology? Penetrating, ionizing…..

Why is too much radiation bad for living things?

 case 1: a cell radiation ionizes the cell wall or other parts and kills the cell  radiation ionizes & breaks the strand on one side - but the DNA repairs itself case 2: DNA - single ionization

  radiation ionizes & breaks the strand - DNA fragments case 3: DNA - multiple ionization rearrangements are possible - a mutation occurs

  radiation ionizes & breaks the strand case 4: DNA - multiple ionization Since break-points are far away, DNA repairs itself

What affect does it have on biology? Mutation….mutagenisis, Cancer….tumorigenisis. Does it make atoms radioactive? No…ionization is a chemical process, not a nuclear process.