Help me out here I don’t understand please :(, ppl srsly answer my questions a week later :/

2. For any given isotope, the sum of the numbers of protons and neutrons in the nucleus is called the mass number.

3. in fact, electron mass is so small that it is not counted in an atom's mass

Explanation:

answers: to make sure that all of the broken pieces of tablet were added to the water, to allow for fair comparison of all three trials, with different particle sizes to avoid experimental error

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.