Final answer:
Noble gases are least likely to form compounds because they have a full valence shell and are highly stable and unreactive.
Step-by-step explanation:
The noble gases, such as helium, neon, and argon, are least likely to form compounds. This is because noble gases have a full valence shell of electrons, making them highly stable and unreactive. They do not readily gain, lose, or share electrons with other elements to achieve a noble gas configuration.