A Scientist mixes a solid powder into a beaker of fluid. Why might the mass be now less than the mass was before they were mixed together?
Would this be an example of a Physical or Chemical Reaction and why?

Explanation is in the file

cutt. ly/lxkFVRg (remove space)

since the atomic number is the number of protons in the nucleus, as we move to the left on the periodic table, the electrostatic pull between the nucleus and the valence electron shell decreases. as we move down a group (vertical column), the valence shell energy level gets further and further from the nucleus.