Which of the following is an example of a scientific law?
a prediction that a reaction will go faster if acid is added to the reaction.
an explanation for why some electrons are affected when they are hit by photons and some electrons are not.
experimental results that show that d = m/v
none of the above

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.