Why can some atoms , such as helium , neon , and argon consist of a collection of individual atoms that move about independently of one another and all other atoms consists of two or more atoms joined by strong forces called chemical bonds ?

The noble gases have been present as an individual atom due to the complete outer valence shell.

In an atom, the presence of valence electrons has been the representation of the reactivity of the atom.

The atoms tend to complete the outermost octet and become stable. In order to be stabilized, the elements form chemical bonds with the same element and have been present in the diatomic form.

However, with noble gases such as Neon, Helium the outer valence shell has been complete, they have been present as individual atoms with less reactivity.

For more information about the chemical bonds, refer to the link:

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Noble gases already have a completed Octet structure hence they are stable.

Explanation:

One basic reason for chemical reaction is that individual atoms seek to attain the stable Octet, that means, to have eight electrons on their outermost shell.

The noble gases are stable since they have already achieved this stable octet structure.

Having already filled electron shells, noble gases hardly participate in chemical bonding but often exist in the gas phase as isolated atoms.