Final answer:
Atoms of main group elements form bonds to achieve a stable electron configuration, often resembling the full outer shells of noble gases. They may gain, lose, or share electrons to fill their outermost energy levels, as seen in the bonding of water molecules.
Step-by-step explanation:
In many compounds, atoms of main group elements form bonds so that the number of electrons in the outermost energy levels of each atom is in line with the octet rule, aiming for a stable configuration similar to that of noble gases. Atoms tend to gain, lose, or share electrons in order to achieve this stable electron configuration. An example of this is the water molecule, where each hydrogen atom shares a pair of electrons with the oxygen atom, resulting in each hydrogen having a full first energy level, and oxygen having a full outer energy level with a total of eight valence electrons.
The process of chemically bonding, whether through ionic or covalent bonds, fulfills the requirement for atoms to have a full valence shell. In the periodic table, the number and arrangement of valence electrons determine the reactive nature of the elements and their ability to form molecules. Hence, the observation that the main group elements form bonds to achieve full outermost energy levels is fundamental to understanding chemical bonding and reactivity.