From the valence electrons of the elements in a compound formed by a reaction, you can predict the bond type between the atoms.
Valence electrons play a crucial role in determining how atoms interact and bond with one another. For instance, if an element has a high number of valence electrons (like halogens), it may tend to gain electrons and form ionic bonds, while elements that can share or lose electrons (like metals) may form covalent bonds. The arrangement of valence electrons also helps in predicting whether bonds will be ionic, covalent, or metallic in nature.