Ido not know why but the answer is 684 let me know why.  a light with a second-order dark band forms a diffraction angle of 20.0°. the diffraction grating has 200.0 lines per mm.the wavelength of the light, to the nearest whole number, is    nm.

4. now look at the green lines you created by connecting the three boiling point data points and the three melting point data points. for each of these lines, describe any trends you see. 5. locate the elements on your periodic table that you circled in green on your graph. what term or description would you use to identify these elements with respect to the periodic table? 7. using the room temperature line (orange line) and your periodic table, make lists that identify the state of matter (gas, liquid, or solid) in which each element you plotted exists at room temperature. explain your answers.