I’m a chemical formula such as h2o what does a small number next to an element symbol tell you

The little number you see to the right of the symbol for an element is called a subscript.

i dont so can you be a little good at asking question

a. energy is absorbed in the reaction.

if in a given reaction the energy of products is greater than the energy of reactants it means that reaction is endothermic and during the reaction, the energy is absorbed by reactants. in an endothermic reaction, the products have more stored chemical energy than the reactants. and in this reaction the reactants are more stable than products before the compounds with less energy are always more stable.