Calcium reacts with oxygen to form calcium oxide. the chemical equation for this reaction is ca + o2 → cao. what is the product, or what are the products, of this reaction?

In any balanced chemical reaction, the elements or compounds which are located in the left hand side of the arrow is the reactants while those that are location on the right hand side are the products, therefore the product here is:

CaO or Calcium Oxide

the seeing the electronic configuration we can say that the element is fluorine.

fluorine is the most electronegative element in the periodic table.

but by only seeing the configuration we cannot say about its reactivity because we don't know if its configuration after excitation or by addition of electrons.

but if not then, it is the lightest halogen and exists as a highly toxic pale yellow diatomic gas at standard conditions. as the most electronegative element, it is extremely reactive: almost all other elements, including some noble gases, form compounds with fluorine.