Chemical reactions primarily depend on valence electrons because these are the electrons involved in the formation and breaking of chemical bonds between atoms. Valence electrons are the outermost electrons in an atom, located in the highest principal energy level (shell). They determine the atom's reactivity and its ability to form bonds with other atoms.
When atoms interact to form molecules or compounds, their valence electrons participate in the sharing, transfer, or redistribution of electrons to achieve a more stable electronic configuration. This process is driven by the tendency of atoms to attain a full outer electron shell, typically by acquiring or sharing electrons.
The valence electrons determine an atom's valency, which indicates the number of bonds an atom can form. For example, elements in Group 1 of the periodic table, such as sodium (Na), have one valence electron and tend to lose that electron to achieve a stable configuration like a noble gas (in this case, like neon). On the other hand, elements in Group 7, like chlorine (Cl), have seven valence electrons and tend to gain one electron to achieve a stable configuration like a noble gas (in this case, like argon).
During a chemical reaction, valence electrons are either shared between atoms in covalent bonding or transferred from one atom to another in ionic bonding. The rearrangement of valence electrons leads to the formation of new chemical bonds or the breaking of existing bonds, resulting in the transformation of reactant molecules into product molecules.
Overall, the reactivity and behavior of atoms in chemical reactions are determined by the interactions of their valence electrons, making them crucial in understanding and predicting the outcomes of chemical reactions.