Do all homoatomic molecules form covalent bonds only

Question

I asked my mom a question if all homoatomic molecules form only with covalent bonds, and she said "yeah, they should most of the time" and I asked her why only most of the time, because I dont get how they can form any other type of bond, but my mom said that there could be an exception.

So I am wondering if there could be a such thing as an exception, because I dont get it, how can the same atoms bond together in any other way.

Answer 1

Atoms which have 4,5,6 or 7 electrons in the outermost shell (have high electronegativity) will form covalent bond(s) between atoms of same element. Highly electronegative atoms will not readily loose electron(s) to make cation, therefore ionic bond formation is not possible. So all homoatomic molecules will have covalent bond between the  bonded atoms.  

Answer 2

That's a sticky subject!  Yes I believe it.  

Answer 3

Yes they always do.

The reason why is that the difference in the electronegativity of both atoms is zero because they both have the same electronegativity.

All bonds with zero difference are covalent.

It would have been better if you Mom had left the phrase "most of the time" and said "always" instead.

Answer 4

Your mom is right.

For example, metal crystals are homoatomic, but they form metallic bonds right?

I feel I must share this too: the ozone molecule is homoatomic but there's a coordinate bond there (but I don't know if that too is classified as a kind of covalent bond, then too it's not like a typical bond between like atoms)