What are valence electrons? The number of neutrons in a nucleus. The number of protons in the nucleus. The atomic mass is the same as the number of valence electrons. The number of electron in the outer most shell of an atom.

Valence Electrons are The number of electrons in the outer most shell of an atom. These shells have a maximum amount before being filled by electrons, in which remaining electrons will fill the next remaining valence shell.

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.