Which of the following is an example of how to supply activation energy to begin a reaction?
a. cool the reaction flask in an ice bath.
b. add a catalyst.
c. heat the reaction flask on a hot plate.
d. add an inhibitor. '

The event that is an example of how to supply activation energy to begin a reaction is adding a catalyst. The answer is letter B. Cooling the reaction flask in an ice bath, heating the reaction flask on a hot plate. And adding an inhibitor does not answer the question.

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.