1. Arrange the following elements in order of increasing (from smallest to largest) atomic size: K,O, Cs, Se. Explain the reasoning behind your chosen order. Do not simply restate the trend, but rather explain why the trend exists.


  1. Potassium has three naturally occurring isotopes. According to one source of data, Potassium-39 (mass 38.9637 amu) makes up 93.26%, potassium-40 (mass 39.9640 amu) makes up just 0.01%, and potassium-41 (mass 40.9618 amu) makes up 6.73%. What is the average atomic mass of potassium based on these relative abundances? Show all your work for credit, and express your final answer to 2 decimal places and include the unit.
Questions CHE 130