The main reason atoms form chemical bonds, according to the Kossel-Lewis approach, is to achieve stable octets in their outermost shells. This concept is rooted in the desire of atoms to attain a stable electronic configuration, similar to that of the noble gases.

Explanation:

• The Kossel-Lewis theory postulates that atoms tend to form bonds in order to complete their outermost shell with eight electrons. This is known as the "octet rule".
• Noble gases naturally have complete outer electron shells, making them extremely stable and unreactive. Other elements seek to replicate this stable configuration through the formation of chemical bonds.
• Atoms can achieve an octet by sharing electrons (covalent bonds), transferring electrons (ionic bonds), or through metallic bonding in metals.

Justification of other options:

• To maximize their energy states always: This is incorrect because atoms form bonds to minimize energy and maximize stability.
• To increase their atomic mass significantly: This is not a reason for forming bonds since bonding does not change atomic mass; it only involves changes in electron configurations.
• To share electrons regardless of stability: Atoms share electrons to achieve stability, not merely to share them without purpose.

Thus, the correct answer is that atoms form chemical bonds to achieve stable octets in their outermost shells.