The power goes out and the only light source you have available is a chemical glow stick. As you sit in the dark with this tiny light source you think
about your lesson on endothermic and exothermic reactions. Do you think
this reaction would be classified as an endothermic or an exothermic reaction?
Be sure to state your evidence and reasoning for your answer.

the answer is c.the valence of the atoms combine .

answer: atomic mass was originally used to arrange elements on the periodic table, but is no longer used to organize the modern version.

explanation:

originally atomic mass was used to arrange elements on the periodic table from left to right in a row. each column then shows similar properties of elements of a group.

in modern periodic table, the atoms are arranged in increasing atomic number. as atomic number represents the number of protons in an atom which is unique for every atom.