State whether each of the following elements is a gas, a liquid, or a solid under atmospheric conditions. Also state whether it exists in the elemental form as atoms, as molecules, or as a three-dimensional network: Mg, Cl, Si, Kr, O, I, Hg, Br

September 1, 2017 – Lecture 4 Nuclear Kinetics dN/dt= counts per s (or min, hr, …) = slope of N vs t Rate equation dN/dt = -kN (k is rate constant) (N is number of counts) d[A]/dt = -k[A] Integrated rate equation Ln{No/N} = kt (amount of time) Ln{[Ao]/[A]} = kt (No or Ao means initial) (denominators = amount at a certain time) The Nuclear Half-Life Rates are commonly given in half-lives, the time required for one-half of a nuclide to decay Ln (No/N) = kt Ln(No/ ½ No) = kt ½ Ln(No/ ½ No) = ln2 = kt ½ Ln 2 = kt 1/2 0.693 K=ln2/ t 1/2r t1/2n2/k Question 1: how long will a cobalt-60 source be useful if it can be used until the gamma rays it produces reach 70 percent of the original intensity 60-27 Co decays with a half-life of 5.3 years to produce 60-28