plz help i really need this

Answer:
The reactivity of metals increases as you move left in a period and as you move down in a group, so Marie needs to know the period and group of the element inside each box. Boxes that show locations in groups 1 or 2 or in period 8 contain the most reactive elements.
Explanation:
Answer:
The Group Number of the elements.
Explanation:
If Marie knew the group number of the elements, then she could determine the amount of valence electrons each element has and their reactivity rate. For example, if one box tells her that an element is located in group 18, then she could determine that the element is not very reactive. This is because elements in group 18 have 8 valence electrons, which makes them stable/unreactive.
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