The following statements apply:
Reactions between atoms occur when:
1. AN ATOM SEEKS TO FILLS ITS OUTER SHELL OF ELECTRONS
2. AN ATOM SEEKS TO BALANCE ITS POSITIVE AND NEGATIVE CHARGES.
Generally, chemical reaction occurs because atoms of elements are looking for a way of attaining the octet structure so that hey will be stable. To attain stability, atom have to fill their outermost shells so that they will have 8 electrons in their valence shells. Chemical reactions can also occur when charged particles want to react together and become neutral.